diff --git a/web/main.js b/web/main.js
index b89e274..8427759 100644
--- a/web/main.js
+++ b/web/main.js
@@ -81,7 +81,23 @@ function createUserItem(user, isMe) {
 function handleClientList(idx, list, selfId) {
   const rd = roomsData[idx];
   if (!rd) return;
- // 更新在线用户列表和映射
+  // 记录旧用户ID集合
+  const oldUserIds = new Set((rd.userList || []).map(u => u.clientId));
+  // 新用户ID集合
+  const newUserIds = new Set(list.map(u => u.clientId));
+  // 检查退出用户（旧有，新没有）
+  if (rd.isInitialized) {
+    for (const oldId of oldUserIds) {
+      if (!newUserIds.has(oldId)) {
+        const user = rd.userMap[oldId];
+        const name = user ? (user.userName || user.username || user.name || 'Anonymous') : 'Anonymous';
+        const msg = `${name}已退出`;
+        rd.messages.push({ type: 'system', text: msg });
+        if (activeRoomIndex === idx) addSystemMsg(msg, true);
+      }
+    }
+  }
+  // 更新在线用户列表和映射
   rd.userList = list;
   rd.userMap = {};
   list.forEach(u => { rd.userMap[u.clientId] = u; });
@@ -98,9 +114,7 @@ function handleClientList(idx, list, selfId) {
     // 基准用户集合
     rd.knownUserIds = new Set(list.map(u => u.clientId));
   }
-
 }
-
 // 调整 handleClientSecured: 立即更新UI，仅在初始化完成后才处理加入提示
 function handleClientSecured(idx, user) {
   const rd = roomsData[idx];