diff --git a/pages/message/chat.scss b/pages/message/chat.scss
index 3b88641..3fe026f 100644
--- a/pages/message/chat.scss
+++ b/pages/message/chat.scss
@@ -401,11 +401,26 @@ $primary-color: #0877F1;
 
 .input-toolbar {
   display: flex;
-  align-items: center;
+  align-items: flex-end;
+  position: relative;
   padding: 16rpx 20rpx;
   gap: 12rpx;
 }
 
+.expand-input-btn {
+  position: absolute;
+  top: 16rpx;
+  left: 20rpx;
+  width: 40rpx;
+  height: 40rpx;
+  z-index: 1;
+
+  image {
+    width: 100%;
+    height: 100%;
+  }
+}
+
 .voice-toggle-btn {
   width: 56rpx;
   height: 56rpx;
@@ -414,6 +429,7 @@ $primary-color: #0877F1;
   justify-content: center;
   flex-shrink: 0;
   padding: 0;
+  margin-bottom: 12rpx;
 }
 
 .voice-toggle-icon {
@@ -432,6 +448,7 @@ $primary-color: #0877F1;
   justify-content: center;
   flex-shrink: 0;
   padding: 0;
+  margin-bottom: 12rpx;
 }
 
 .send-btn {
@@ -451,6 +468,7 @@ $primary-color: #0877F1;
   transition: background 0.2s;
   flex-shrink: 0;
   white-space: nowrap;
+  margin-bottom: 12rpx;
 }
 
 .send-btn:active {
@@ -509,6 +527,7 @@ $primary-color: #0877F1;
   display: block;
   line-height: 1.5;
   height: 80rpx;
+  max-height: 500rpx;
 }
 
 .voice-input-btn {
@@ -521,6 +540,46 @@ $primary-color: #0877F1;
   line-height: 80rpx;
 }
 
+.expanded-input-overlay {
+  position: fixed;
+  inset: 0;
+  z-index: 1000;
+  display: flex;
+  flex-direction: column;
+  background: #fff;
+  border-radius: 24rpx 24rpx 0 0;
+  overflow: hidden;
+}
+
+.expanded-input-header {
+  height: 96rpx;
+  flex-shrink: 0;
+  padding: 24rpx 24rpx 0;
+  box-sizing: border-box;
+}
+
+.collapse-input-btn {
+  width: 40rpx;
+  height: 40rpx;
+
+  image {
+    width: 100%;
+    height: 100%;
+  }
+}
+
+.expanded-text-input {
+  flex: 1;
+  min-height: 0;
+  width: 100%;
+  padding: 0 32rpx 32rpx;
+  box-sizing: border-box;
+  font-size: 30rpx;
+  line-height: 1.5;
+  color: #333;
+  background: #fff;
+}
+
 .more-panel {
   display: flex;
   justify-content: flex-start;
diff --git a/pages/message/components/chat-input.vue b/pages/message/components/chat-input.vue
index 0c7db56..c4d912a 100644
--- a/pages/message/components/chat-input.vue
+++ b/pages/message/components/chat-input.vue
@@ -6,6 +6,9 @@
     </view>
 
     <view class="input-toolbar">
+      <view v-if="showExpandButton" class="expand-input-btn" @click="expandInput">
+        <image src="/static/expand.svg" mode="aspectFit"></image>
+      </view>
       <view @click="toggleVoiceInput" class="voice-toggle-btn">
         <image v-if="showVoiceInput" src="/static/jianpan.png" class="voice-toggle-icon" mode="aspectFit"></image>
         <uni-icons v-else type="mic" size="28" color="#666" />
@@ -14,7 +17,7 @@
         <!-- :hold-keyboard="true" -->
         <textarea v-if="!showVoiceInput" class="text-input" v-model="inputText" placeholder="我来说两句..."
           @confirm="sendTextMessage" @focus="handleInputFocus" @input="handleInput" :auto-height="true"
-          :show-confirm-bar="false" :maxlength="-1" :cursor-spacing="40" ref="textareaRef" />
+          :show-confirm-bar="false" :maxlength="-1" :cursor-spacing="40" :focus="normalTextareaFocus" ref="textareaRef" />
         <input v-else class="voice-input-btn" :class="{ recording: isRecording }" @touchstart="startRecord"
           @touchmove="onRecordTouchMove" @touchend="stopRecord" @touchcancel="cancelRecord"
           :placeholder="isRecording ? '松开发送' : '按住说话'" disabled />
@@ -29,6 +32,16 @@
         <text>生成中...</text>
       </view>
     </view>
+    <view v-if="isInputExpanded" class="expanded-input-overlay">
+      <view class="expanded-input-header">
+        <view class="collapse-input-btn" @click="collapseInput">
+          <image src="/static/mini.svg" mode="aspectFit"></image>
+        </view>
+      </view>
+      <textarea class="expanded-text-input" v-model="inputText" placeholder="我来说两句..."
+        @confirm="sendTextMessage" @focus="handleInputFocus" @input="handleInput" :auto-height="false"
+        :show-confirm-bar="false" :maxlength="-1" :cursor-spacing="40" :focus="expandedTextareaFocus" />
+    </view>
     <view class="more-panel" v-if="showMorePanel">
       <view v-for="btn in morePanelButtons" :key="btn.text" class="more-btn" @click="btn.action">
         <image :src="btn.icon" class="more-icon" mode="aspectFit"></image>
@@ -62,7 +75,7 @@
 </template>
 
 <script setup>
-import { computed, ref, onMounted, onUnmounted, nextTick } from "vue";
+import { computed, getCurrentInstance, ref, onMounted, onUnmounted, nextTick, watch } from "vue";
 import {
   chooseImage,
   takePhoto as takePhotoUtil,
@@ -108,6 +121,13 @@ const showMorePanel = ref(false);
 const isRecording = ref(false);
 const recordingText = ref("录音中...");
 const textareaRef = ref(null);
+const isInputExpanded = ref(false);
+const isInputOverFourLines = ref(false);
+const singleLineInputHeight = ref(0);
+const normalTextareaFocus = ref(false);
+const expandedTextareaFocus = ref(false);
+const instanceProxy = getCurrentInstance()?.proxy;
+const showExpandButton = computed(() => !showVoiceInput.value && isInputOverFourLines.value && !isInputExpanded.value);
 const cloudCustomData = computed(() => {
   const arr = [
     props.chatRoomBusiness.businessType,
@@ -121,6 +141,55 @@ const appendStreamText = (char) => {
   inputText.value += char;
 };
 
+const updateInputLines = async () => {
+  await nextTick();
+  if (showVoiceInput.value || isInputExpanded.value) return;
+
+  const hasExplicitLineBreak = /[\r\n]/.test(inputText.value);
+  if (hasExplicitLineBreak) {
+    const inputLineCount = inputText.value.split(/\r\n|\r|\n/).length;
+    isInputOverFourLines.value = inputLineCount > 4;
+    return;
+  }
+
+  if (inputText.value.length <= 1 && singleLineInputHeight.value) {
+    isInputOverFourLines.value = false;
+    return;
+  }
+
+  const query = instanceProxy ? uni.createSelectorQuery().in(instanceProxy) : uni.createSelectorQuery();
+  query.select(".text-input").boundingClientRect();
+  query.exec((res) => {
+    const inputRect = res && res[0];
+    if (!inputRect) return;
+
+    if (!singleLineInputHeight.value) singleLineInputHeight.value = inputRect.height;
+
+    const lineHeight = (45 * uni.getSystemInfoSync().windowWidth) / 750;
+    const fourLineHeight = singleLineInputHeight.value + lineHeight * 3;
+    isInputOverFourLines.value = inputRect.height > fourLineHeight + 1;
+  });
+};
+
+const expandInput = () => {
+  normalTextareaFocus.value = false;
+  isInputExpanded.value = true;
+  nextTick(() => {
+    expandedTextareaFocus.value = true;
+  });
+};
+
+const collapseInput = () => {
+  expandedTextareaFocus.value = false;
+  isInputExpanded.value = false;
+  nextTick(() => {
+    normalTextareaFocus.value = true;
+    updateInputLines();
+  });
+};
+
+watch(inputText, updateInputLines);
+
 // 录音相关扩展状态（特效 + 取消逻辑）
 const recordingDuration = ref(0);
 let recordingTimer = null;
@@ -329,11 +398,14 @@ const sendCustomMessage = async (messageData) => {
 const toggleVoiceInput = () => {
   showVoiceInput.value = !showVoiceInput.value;
   showMorePanel.value = false;
+  if (!showVoiceInput.value) updateInputLines();
 };
 
 const toggleMorePanel = () => {
   showMorePanel.value = !showMorePanel.value;
+  const wasVoiceInput = showVoiceInput.value;
   showVoiceInput.value = false;
+  if (wasVoiceInput) updateInputLines();
 };
 
 // 处理图片选择
@@ -590,7 +662,6 @@ function handleInputFocus() {
 }
 
 function handleInput(e) {
-  // textarea 输入时触发，可以在这里处理额外逻辑
   nextTick().then(() => {
     emit("scrollToBottom");
   });
@@ -599,6 +670,7 @@ function handleInput(e) {
 onMounted(() => {
   // 初始化录音管理器
   initRecorderManager();
+  updateInputLines();
 
   // 监听关闭功能栏事件
   uni.$on("closeMorePanel", () => {
diff --git a/static/expand.svg b/static/expand.svg
new file mode 100644
index 0000000..d274df1
--- /dev/null
+++ b/static/expand.svg
@@ -0,0 +1 @@
+<?xml version="1.0" standalone="no"?><!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd"><svg t="1792130980667" class="icon" viewBox="0 0 1024 1024" version="1.1" xmlns="http://www.w3.org/2000/svg" p-id="1700" xmlns:xlink="http://www.w3.org/1999/xlink" width="200" height="200"><path d="M459.712 507.568L208 759.28V528H128v368h368v-80H264.56l251.728-251.792-56.576-56.64zM528 128v80h231.44L507.712 459.712l56.576 56.576L816 264.56V496h80V128H528z" fill="#565D64" p-id="1701"></path></svg>
\ No newline at end of file
diff --git a/static/mini.svg b/static/mini.svg
new file mode 100644
index 0000000..885296c
--- /dev/null
+++ b/static/mini.svg
@@ -0,0 +1 @@
+<?xml version="1.0" standalone="no"?><!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd"><svg t="1792131033804" class="icon" viewBox="0 0 1024 1024" version="1.1" xmlns="http://www.w3.org/2000/svg" p-id="3515" xmlns:xlink="http://www.w3.org/1999/xlink" width="200" height="200"><path d="M104.704 338.752a64 64 0 0 1 90.496 0L512 655.552l316.8-316.8a64 64 0 0 1 90.496 90.496l-362.048 362.048a64 64 0 0 1-90.496 0L104.704 429.248a64 64 0 0 1 0-90.496z" p-id="3516"></path></svg>
\ No newline at end of file