diff --git a/frontend/src/views/machine/MachineListPage.vue b/frontend/src/views/machine/MachineListPage.vue
index b4f8f9f..366010b 100644
--- a/frontend/src/views/machine/MachineListPage.vue
+++ b/frontend/src/views/machine/MachineListPage.vue
@@ -48,8 +48,7 @@
       <el-table-column prop="ipAddress" label="IP地址" />
       <el-table-column label="在线状态" align="center">
         <template #default="{ row }">
-          <el-tag :type="row.isOnline ? 'success' : 'info'" size="small">{{ row.isOnline ? '在线' : '离线' }}</el-tag>
-          <span v-if="row.isOnline && row.lastPingLatency != null" style="margin-left:4px;font-size:12px;color:#909399">{{ row.lastPingLatency }}ms</span>
+          <el-tag :type="row.isOnline ? 'success' : 'info'" size="small">{{ row.isOnline ? '在线' : '离线' }}{{ row.lastPingLatency != null ? `-${row.lastPingLatency}ms` : '' }}</el-tag>
         </template>
       </el-table-column>
       <el-table-column label="状态" align="center">
diff --git a/src/CncCollector/Core/CollectWorker.cs b/src/CncCollector/Core/CollectWorker.cs
index b7d4450..c723f03 100644
--- a/src/CncCollector/Core/CollectWorker.cs
+++ b/src/CncCollector/Core/CollectWorker.cs
@@ -253,10 +253,10 @@ namespace CncCollector.Core
                         conn.Execute(@"UPDATE cnc_machine SET last_ping_time = NOW(), last_ping_latency = @Latency, updated_at = NOW() WHERE id = @Id",
                             new { Id = kv.Key, Latency = kv.Value });
                     }
-                    // 离线机床：清空延迟，不更新 last_ping_time
+                    // 离线机床：不更新 last_ping_time，保留上次延迟值
                     if (offlineIds.Count > 0)
                     {
-                        conn.Execute(@"UPDATE cnc_machine SET last_ping_latency = NULL, updated_at = NOW() WHERE id IN @Ids",
+                        conn.Execute(@"UPDATE cnc_machine SET updated_at = NOW() WHERE id IN @Ids",
                             new { Ids = offlineIds });
                     }
                 }