diff --git a/Apewer.Windows/WinForm/Tray.cs b/Apewer.Windows/WinForm/Tray.cs
index 4a303af..436e3fd 100644
--- a/Apewer.Windows/WinForm/Tray.cs
+++ b/Apewer.Windows/WinForm/Tray.cs
@@ -311,16 +311,22 @@ namespace Apewer.WinForm
 
         #region run
 
+        /// <summary>唯一实例。</summary>
+        public static Tray Instance { get; private set; }
+
         /// <summary>已启动的服务名称。</summary>
         public static string ServiceName { get; private set; }
 
-        /// <summary>在当前线程运行托盘程序，并启动消息循环。</summary>
-        /// <param name="action">启动托盘后执行的程序。</param>
+        /// <summary>在当前线程运行托盘程序，并启动消息循环。此方法应在主线程中调用，并且此方法将阻塞当前线程。</summary>
+        /// <remarks>托盘启动后，将在后台线程执行参数中指定的程序。</remarks>
+        /// <param name="action">（在后台线程执行）启动托盘后执行的程序。</param>
         /// <exception cref="ArgumentNullException" />
+        /// <exception cref="InvalidOperationException" />
         [STAThread]
         public static void Run(Action<Tray> action)
         {
             if (action == null) throw new ArgumentNullException(nameof(action));
+            if (Instance != null) throw new InvalidOperationException($"已存在实例，无法再次启动。");
 
             Control.CheckForIllegalCrossThreadCalls = false;
             Application.EnableVisualStyles();
@@ -337,14 +343,14 @@ namespace Apewer.WinForm
                 }
             }
 
-            var instance = new Tray(action);
+            Instance = new Tray(action);
             // action.Invoke(instance);
             Application.Run();
         }
 
         /// <summary>启动服务。</summary>
-        /// <param name="onStart">服务启动后执行的程序。</param>
-        /// <param name="onStop">停止服务时执行的程序。</param>
+        /// <param name="onStart">（在后台线程执行）服务启动后执行的程序。</param>
+        /// <param name="onStop">（同步执行）停止服务时执行的程序。</param>
         public static void Service(Action onStart, Action onStop = null)
         {
             var processName = Process.GetCurrentProcess().ProcessName;