diff --git a/apps/desktop/src/components/mqtt/MqttPublishDialog.vue b/apps/desktop/src/components/mqtt/MqttPublishDialog.vue
index 68d2373857..0f7c53b3c6 100644
--- a/apps/desktop/src/components/mqtt/MqttPublishDialog.vue
+++ b/apps/desktop/src/components/mqtt/MqttPublishDialog.vue
@@ -1,5 +1,5 @@
 <script setup lang="ts">
-import { computed, ref, watch } from "vue";
+import { computed, onMounted, onUnmounted, ref, watch } from "vue";
 import { useI18n } from "vue-i18n";
 import { mqttPublish } from "@/lib/backend/api";
 import { Button } from "@/components/ui/button";
@@ -24,6 +24,18 @@ const encoding = ref<PayloadEncoding>("plaintext");
 const loading = ref(false);
 const error = ref<string | null>(null);
 const success = ref(false);
+const publishPanelRef = ref<HTMLElement | null>(null);
+const payloadTextareaRef = ref<HTMLTextAreaElement | null>(null);
+const payloadHeight = ref(80);
+const resizing = ref(false);
+
+const MQTT_PAYLOAD_MIN_HEIGHT_PX = 60;
+const MQTT_PAYLOAD_MAX_PANEL_RATIO = 0.5;
+const MQTT_PAYLOAD_KEYBOARD_STEP_PX = 10;
+const MQTT_PAYLOAD_HEIGHT_STORAGE_KEY = "dbx-mqtt-payload-height";
+let resizeStartY = 0;
+let resizeStartHeight = 0;
+let panelResizeObserver: ResizeObserver | undefined;
 
 const qosLabels = ["QoS 0", "QoS 1", "QoS 2"];
 const qosHints = computed(() => [t("connection.mqttQosAtMostOnce"), t("connection.mqttQosAtLeastOnce"), t("connection.mqttQosExactlyOnce")]);
@@ -55,6 +67,89 @@ watch(
   },
 );
 
+/** 计算消息输入框允许使用的最大高度，避免挤占全部消息列表区域 */
+function maxPayloadHeight() {
+  const containerHeight = publishPanelRef.value?.parentElement?.clientHeight || window.innerHeight || 0;
+  const panelHeight = publishPanelRef.value?.offsetHeight || 0;
+  const currentTextareaHeight = payloadTextareaRef.value?.offsetHeight || payloadHeight.value;
+  const panelChromeHeight = Math.max(0, panelHeight - currentTextareaHeight);
+  return Math.max(MQTT_PAYLOAD_MIN_HEIGHT_PX, Math.floor(containerHeight * MQTT_PAYLOAD_MAX_PANEL_RATIO - panelChromeHeight));
+}
+
+/** 将消息输入框高度限制在可用区域内 */
+function clampPayloadHeight(height: number) {
+  return Math.max(MQTT_PAYLOAD_MIN_HEIGHT_PX, Math.min(maxPayloadHeight(), Math.round(height)));
+}
+
+function persistPayloadHeight(height: number) {
+  payloadHeight.value = clampPayloadHeight(height);
+  localStorage.setItem(MQTT_PAYLOAD_HEIGHT_STORAGE_KEY, payloadHeight.value.toString());
+}
+
+/** 容器尺寸变化时同步收缩输入框，保证消息列表仍可见 */
+function handlePanelResize() {
+  payloadHeight.value = clampPayloadHeight(payloadHeight.value);
+}
+
+/** 开始拖动消息输入框顶部的高度调节条 */
+function startResize(event: MouseEvent) {
+  event.preventDefault();
+  resizing.value = true;
+  resizeStartY = event.clientY;
+  resizeStartHeight = payloadHeight.value;
+
+  document.addEventListener("mousemove", handleResize);
+  document.addEventListener("mouseup", stopResize);
+  document.body.style.userSelect = "none";
+  document.body.style.cursor = "ns-resize";
+}
+
+/** 根据向上拖动的距离实时调整消息输入框高度 */
+function handleResize(event: MouseEvent) {
+  if (!resizing.value) return;
+  payloadHeight.value = clampPayloadHeight(resizeStartHeight + resizeStartY - event.clientY);
+}
+
+function handleResizeKeydown(event: KeyboardEvent) {
+  const direction = event.key === "ArrowUp" ? 1 : event.key === "ArrowDown" ? -1 : 0;
+  if (direction === 0) return;
+  event.preventDefault();
+  persistPayloadHeight(payloadHeight.value + direction * MQTT_PAYLOAD_KEYBOARD_STEP_PX);
+}
+
+/** 结束拖动并记住用户设置的高度 */
+function stopResize() {
+  if (!resizing.value) return;
+  resizing.value = false;
+  document.removeEventListener("mousemove", handleResize);
+  document.removeEventListener("mouseup", stopResize);
+  document.body.style.userSelect = "";
+  document.body.style.cursor = "";
+  persistPayloadHeight(payloadHeight.value);
+}
+
+onMounted(() => {
+  const savedHeight = Number.parseInt(localStorage.getItem(MQTT_PAYLOAD_HEIGHT_STORAGE_KEY) ?? "", 10);
+  if (Number.isFinite(savedHeight)) payloadHeight.value = clampPayloadHeight(savedHeight);
+
+  window.addEventListener("resize", handlePanelResize);
+  if (typeof ResizeObserver !== "undefined" && publishPanelRef.value?.parentElement) {
+    panelResizeObserver = new ResizeObserver(handlePanelResize);
+    panelResizeObserver.observe(publishPanelRef.value.parentElement);
+  }
+});
+
+onUnmounted(() => {
+  document.removeEventListener("mousemove", handleResize);
+  document.removeEventListener("mouseup", stopResize);
+  window.removeEventListener("resize", handlePanelResize);
+  panelResizeObserver?.disconnect();
+  if (resizing.value) {
+    document.body.style.userSelect = "";
+    document.body.style.cursor = "";
+  }
+});
+
 async function publish() {
   const publishTopic = topic.value.trim();
   if (!publishTopic) {
@@ -102,7 +197,20 @@ function clearForm() {
 </script>
 
 <template>
-  <div class="publish-panel">
+  <div ref="publishPanelRef" class="publish-panel">
+    <div
+      class="payload-resize-handle"
+      role="separator"
+      tabindex="0"
+      aria-orientation="horizontal"
+      :aria-label="t('connection.mqttResizePayload')"
+      :aria-valuemin="MQTT_PAYLOAD_MIN_HEIGHT_PX"
+      :aria-valuemax="maxPayloadHeight()"
+      :aria-valuenow="payloadHeight"
+      :title="t('connection.mqttResizePayload')"
+      @mousedown="startResize"
+      @keydown="handleResizeKeydown"
+    />
     <div class="panel-header">
       <span class="panel-title">{{ t("connection.mqttPublish") }}</span>
       <Button size="sm" variant="ghost" class="h-6 text-xs" @click="clearForm">{{ t("common.clear") }}</Button>
@@ -150,7 +258,7 @@ function clearForm() {
     <!-- Payload -->
     <div class="form-group flex-1 flex flex-col min-h-0">
       <label class="form-label">{{ t("connection.mqttPayload") }}</label>
-      <textarea v-model="payloadText" class="form-textarea flex-1 font-mono text-xs" :placeholder="payloadPlaceholder" rows="4" @keydown.ctrl.enter="publish()" />
+      <textarea ref="payloadTextareaRef" v-model="payloadText" class="form-textarea font-mono text-xs" :style="{ height: `${payloadHeight}px`, maxHeight: `${maxPayloadHeight()}px` }" :placeholder="payloadPlaceholder" @keydown.ctrl.enter="publish()" />
       <span class="form-hint">{{ t("connection.mqttPublishShortcut") }}</span>
     </div>
 
@@ -169,6 +277,7 @@ function clearForm() {
 
 <style scoped>
 .publish-panel {
+  position: relative;
   display: flex;
   flex-direction: column;
   gap: 8px;
@@ -177,6 +286,37 @@ function clearForm() {
   background: var(--color-background);
 }
 
+.payload-resize-handle {
+  position: absolute;
+  top: -4px;
+  left: 0;
+  right: 0;
+  z-index: 1;
+  height: 9px;
+  cursor: ns-resize;
+}
+
+.payload-resize-handle::before {
+  content: "";
+  position: absolute;
+  top: 3px;
+  left: 0;
+  right: 0;
+  height: 1px;
+  background-color: var(--color-border);
+  transition: background-color 0.15s ease;
+}
+
+.payload-resize-handle:hover::before,
+.payload-resize-handle:focus-visible::before {
+  background-color: color-mix(in srgb, var(--color-text) 20%, transparent);
+}
+
+.payload-resize-handle:focus-visible {
+  outline: 2px solid var(--color-primary);
+  outline-offset: -2px;
+}
+
 .panel-header {
   display: flex;
   align-items: center;
@@ -240,7 +380,7 @@ function clearForm() {
   background: var(--color-background);
   color: var(--color-text);
   outline: none;
-  resize: vertical;
+  resize: none;
   min-height: 60px;
   box-sizing: border-box;
   line-height: 1.4;
diff --git a/apps/desktop/src/components/mqtt/__tests__/MqttPublishDialog.spec.ts b/apps/desktop/src/components/mqtt/__tests__/MqttPublishDialog.spec.ts
new file mode 100644
index 0000000000..d636a051ad
--- /dev/null
+++ b/apps/desktop/src/components/mqtt/__tests__/MqttPublishDialog.spec.ts
@@ -0,0 +1,108 @@
+// @vitest-environment happy-dom
+
+import { createApp, nextTick, type App } from "vue";
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
+import i18n, { loadLocaleMessages } from "@/i18n";
+import MqttPublishDialog from "@/components/mqtt/MqttPublishDialog.vue";
+
+const { mqttPublishMock } = vi.hoisted(() => ({
+  mqttPublishMock: vi.fn(),
+}));
+
+vi.mock("@/lib/backend/api", () => ({
+  mqttPublish: mqttPublishMock,
+}));
+
+const mountedApps: App[] = [];
+
+async function mountPublishDialog() {
+  const container = document.createElement("div");
+  document.body.append(container);
+  const app = createApp(MqttPublishDialog, {
+    connectionId: "mqtt-connection-1",
+    initialTopic: "device/status",
+  });
+  mountedApps.push(app);
+  app.use(i18n);
+  app.mount(container);
+  await nextTick();
+  return container;
+}
+
+beforeEach(async () => {
+  mqttPublishMock.mockReset().mockResolvedValue(undefined);
+  localStorage.clear();
+  await loadLocaleMessages("zh-CN");
+  i18n.global.locale.value = "zh-CN";
+});
+
+afterEach(() => {
+  for (const app of mountedApps.splice(0)) app.unmount();
+  document.body.innerHTML = "";
+  localStorage.clear();
+});
+
+describe("MQTT 消息发布输入框", () => {
+  it("支持从顶部拖动调节高度并记住设置", async () => {
+    const container = await mountPublishDialog();
+    const handle = container.querySelector<HTMLElement>(".payload-resize-handle");
+    const textarea = container.querySelector<HTMLTextAreaElement>("textarea");
+    expect(handle?.getAttribute("aria-label")).toBe("拖动调节消息输入框高度");
+    expect(handle?.getAttribute("role")).toBe("separator");
+    expect(handle?.getAttribute("aria-orientation")).toBe("horizontal");
+
+    handle?.dispatchEvent(new MouseEvent("mousedown", { bubbles: true, clientY: 300 }));
+    document.dispatchEvent(new MouseEvent("mousemove", { bubbles: true, clientY: 180 }));
+    document.dispatchEvent(new MouseEvent("mouseup", { bubbles: true, clientY: 180 }));
+    await nextTick();
+
+    expect(textarea?.style.height).toBe("200px");
+    expect(localStorage.getItem("dbx-mqtt-payload-height")).toBe("200");
+  });
+
+  it("支持键盘调节高度并记住设置", async () => {
+    const container = await mountPublishDialog();
+    const handle = container.querySelector<HTMLElement>(".payload-resize-handle");
+    const textarea = container.querySelector<HTMLTextAreaElement>("textarea");
+
+    expect(handle?.tabIndex).toBe(0);
+    handle?.focus();
+    expect(document.activeElement).toBe(handle);
+
+    handle?.dispatchEvent(new KeyboardEvent("keydown", { bubbles: true, cancelable: true, key: "ArrowUp" }));
+    await nextTick();
+
+    expect(textarea?.style.height).toBe("90px");
+    expect(handle?.getAttribute("aria-valuenow")).toBe("90");
+    expect(localStorage.getItem("dbx-mqtt-payload-height")).toBe("90");
+
+    handle?.dispatchEvent(new KeyboardEvent("keydown", { bubbles: true, cancelable: true, key: "ArrowDown" }));
+    await nextTick();
+
+    expect(textarea?.style.height).toBe("80px");
+    expect(handle?.getAttribute("aria-valuenow")).toBe("80");
+    expect(localStorage.getItem("dbx-mqtt-payload-height")).toBe("80");
+  });
+
+  it("将键盘调节限制在分隔条声明的高度范围内", async () => {
+    const container = await mountPublishDialog();
+    const handle = container.querySelector<HTMLElement>(".payload-resize-handle");
+    const textarea = container.querySelector<HTMLTextAreaElement>("textarea");
+    const minHeight = Number(handle?.getAttribute("aria-valuemin"));
+    const maxHeight = Number(handle?.getAttribute("aria-valuemax"));
+
+    for (let i = 0; i < 100; i++) handle?.dispatchEvent(new KeyboardEvent("keydown", { bubbles: true, key: "ArrowDown" }));
+    await nextTick();
+
+    expect(textarea?.style.height).toBe(`${minHeight}px`);
+    expect(handle?.getAttribute("aria-valuenow")).toBe(minHeight.toString());
+    expect(localStorage.getItem("dbx-mqtt-payload-height")).toBe(minHeight.toString());
+
+    for (let i = 0; i < 100; i++) handle?.dispatchEvent(new KeyboardEvent("keydown", { bubbles: true, key: "ArrowUp" }));
+    await nextTick();
+
+    expect(textarea?.style.height).toBe(`${maxHeight}px`);
+    expect(handle?.getAttribute("aria-valuenow")).toBe(maxHeight.toString());
+    expect(localStorage.getItem("dbx-mqtt-payload-height")).toBe(maxHeight.toString());
+  });
+});
diff --git a/apps/desktop/src/i18n/locales/en.ts b/apps/desktop/src/i18n/locales/en.ts
index a64a1259f4..feee6c3be7 100644
--- a/apps/desktop/src/i18n/locales/en.ts
+++ b/apps/desktop/src/i18n/locales/en.ts
@@ -804,6 +804,7 @@ export default {
     mqttRetainMessage: "Retain message",
     mqttPayloadEncoding: "Payload encoding",
     mqttPayload: "Payload",
+    mqttResizePayload: "Drag to resize the message input",
     mqttPayloadPlaceholderPlaintext: "Enter message content...",
     mqttPayloadPlaceholderJson: "Enter JSON, for example {example}",
     mqttPayloadPlaceholderBase64: "Enter Base64-encoded data",
diff --git a/apps/desktop/src/i18n/locales/es.ts b/apps/desktop/src/i18n/locales/es.ts
index f2b3627121..fffce3de1f 100644
--- a/apps/desktop/src/i18n/locales/es.ts
+++ b/apps/desktop/src/i18n/locales/es.ts
@@ -1036,6 +1036,7 @@ export default withEnglishFallback({
     mqttRetainMessage: "Retener mensaje",
     mqttPayloadEncoding: "Codificación del Payload",
     mqttPayload: "Payload",
+    mqttResizePayload: "Arrastra para ajustar la altura del campo de mensaje",
     mqttPayloadPlaceholderPlaintext: "Introduce el contenido del mensaje...",
     mqttPayloadPlaceholderJson: "Introduce JSON, por ejemplo {example}",
     mqttPayloadPlaceholderBase64: "Introduce datos codificados en Base64",
diff --git a/apps/desktop/src/i18n/locales/it.ts b/apps/desktop/src/i18n/locales/it.ts
index 7d825b0d34..6c2b9fc678 100644
--- a/apps/desktop/src/i18n/locales/it.ts
+++ b/apps/desktop/src/i18n/locales/it.ts
@@ -1034,6 +1034,7 @@ export default withEnglishFallback({
     mqttRetainMessage: "Mantieni messaggio",
     mqttPayloadEncoding: "Codifica del Payload",
     mqttPayload: "Payload",
+    mqttResizePayload: "Trascina per regolare l'altezza del campo messaggio",
     mqttPayloadPlaceholderPlaintext: "Inserisci il contenuto del messaggio...",
     mqttPayloadPlaceholderJson: "Inserisci JSON, ad esempio {example}",
     mqttPayloadPlaceholderBase64: "Inserisci dati codificati in Base64",
diff --git a/apps/desktop/src/i18n/locales/ja.ts b/apps/desktop/src/i18n/locales/ja.ts
index 1cab150621..987b3d4958 100644
--- a/apps/desktop/src/i18n/locales/ja.ts
+++ b/apps/desktop/src/i18n/locales/ja.ts
@@ -1034,6 +1034,7 @@ export default withEnglishFallback({
     mqttRetainMessage: "メッセージを保持",
     mqttPayloadEncoding: "ペイロードのエンコード",
     mqttPayload: "ペイロード",
+    mqttResizePayload: "ドラッグしてメッセージ入力欄の高さを調整",
     mqttPayloadPlaceholderPlaintext: "メッセージ内容を入力...",
     mqttPayloadPlaceholderJson: "JSON を入力（例: {example}）",
     mqttPayloadPlaceholderBase64: "Base64 エンコード済みデータを入力",
diff --git a/apps/desktop/src/i18n/locales/pt-BR.ts b/apps/desktop/src/i18n/locales/pt-BR.ts
index 31c436134b..a9d5ac6818 100644
--- a/apps/desktop/src/i18n/locales/pt-BR.ts
+++ b/apps/desktop/src/i18n/locales/pt-BR.ts
@@ -1035,6 +1035,7 @@ export default withEnglishFallback({
     mqttRetainMessage: "Reter mensagem",
     mqttPayloadEncoding: "Codificação do Payload",
     mqttPayload: "Payload",
+    mqttResizePayload: "Arraste para ajustar a altura do campo de mensagem",
     mqttPayloadPlaceholderPlaintext: "Digite o conteúdo da mensagem...",
     mqttPayloadPlaceholderJson: "Digite JSON, por exemplo {example}",
     mqttPayloadPlaceholderBase64: "Digite dados codificados em Base64",
diff --git a/apps/desktop/src/i18n/locales/zh-CN.ts b/apps/desktop/src/i18n/locales/zh-CN.ts
index 5ba41fe445..91397b78dd 100644
--- a/apps/desktop/src/i18n/locales/zh-CN.ts
+++ b/apps/desktop/src/i18n/locales/zh-CN.ts
@@ -729,6 +729,7 @@ export default withEnglishFallback({
     mqttRetainMessage: "保留消息",
     mqttPayloadEncoding: "Payload 编码",
     mqttPayload: "消息内容 (Payload)",
+    mqttResizePayload: "拖动调节消息输入框高度",
     mqttPayloadPlaceholderPlaintext: "输入消息内容...",
     mqttPayloadPlaceholderJson: "输入 JSON，例如 {example}",
     mqttPayloadPlaceholderBase64: "输入 Base64 编码的数据",
diff --git a/apps/desktop/src/i18n/locales/zh-TW.ts b/apps/desktop/src/i18n/locales/zh-TW.ts
index 85fdcafd1a..d135fc8b26 100644
--- a/apps/desktop/src/i18n/locales/zh-TW.ts
+++ b/apps/desktop/src/i18n/locales/zh-TW.ts
@@ -1034,6 +1034,7 @@ export default withEnglishFallback({
     mqttRetainMessage: "保留訊息",
     mqttPayloadEncoding: "Payload 編碼",
     mqttPayload: "訊息內容 (Payload)",
+    mqttResizePayload: "拖曳調整訊息輸入框高度",
     mqttPayloadPlaceholderPlaintext: "輸入訊息內容...",
     mqttPayloadPlaceholderJson: "輸入 JSON，例如 {example}",
     mqttPayloadPlaceholderBase64: "輸入 Base64 編碼的資料",
diff --git a/packages/app-tests/mqttPayloadCodec.test.ts b/packages/app-tests/mqttPayloadCodec.test.ts
index dc46a79ff0..b0bd594ace 100644
--- a/packages/app-tests/mqttPayloadCodec.test.ts
+++ b/packages/app-tests/mqttPayloadCodec.test.ts
@@ -54,6 +54,11 @@ test("MQTT JSON publishing sends canonical bytes instead of the original text",
   assert.match(source, /payloadText:\s*encoding\.value === "plaintext" \? payloadText\.value : null/);
   assert.doesNotMatch(source, /encoding\.value === "plaintext" \|\| encoding\.value === "json"/);
 });
+
+test("MQTT 中文 JSON Payload 保留 UTF-8 文本且不添加换行符", () => {
+  const encoded = encodePayload('{\n  "消息": "温度正常",\n  "设备": "客厅传感器"\n}', "json");
+  assert.equal(decodePayload(encoded, "plaintext"), '{"消息":"温度正常","设备":"客厅传感器"}');
+});
 test("MQTT JSON placeholder uses a named interpolation for literal braces", () => {
   const source = readFileSync("apps/desktop/src/components/mqtt/MqttPublishDialog.vue", "utf8");
   assert.match(source, /mqttPayloadPlaceholderJson", \{ example:/);