diff --git a/Modbus.Net/Modbus.Net/Controller/BaseController.cs b/Modbus.Net/Modbus.Net/Controller/BaseController.cs
index c2491bc..38cc46b 100644
--- a/Modbus.Net/Modbus.Net/Controller/BaseController.cs
+++ b/Modbus.Net/Modbus.Net/Controller/BaseController.cs
@@ -24,7 +24,7 @@ namespace Modbus.Net
         /// <summary>
         ///     消息维护线程是否在运行
         /// </summary>
-        public virtual bool IsSending => SendingThread.Status.Equals(TaskStatus.Running);
+        public virtual bool? IsSending => SendingThread?.Status.Equals(TaskStatus.Running);
 
         /// <summary>
         ///     包切分位置函数
@@ -76,7 +76,7 @@ namespace Modbus.Net
         /// <inheritdoc />
         public virtual void SendStart()
         {
-            if (!IsSending)
+            if (IsSending != true)
             {
                 SendingThread = Task.Run(() => SendingMessageControlInner());
             }
diff --git a/Modbus.Net/Modbus.Net/Controller/MatchDirectlySendController.cs b/Modbus.Net/Modbus.Net/Controller/MatchDirectlySendController.cs
index b6e1627..7401a7c 100644
--- a/Modbus.Net/Modbus.Net/Controller/MatchDirectlySendController.cs
+++ b/Modbus.Net/Modbus.Net/Controller/MatchDirectlySendController.cs
@@ -11,7 +11,7 @@ namespace Modbus.Net
         /// <summary>
         ///     娑堟伅缁存姢绾跨▼鏄惁鍦ㄨ繍琛�
         /// </summary>
-        public override bool IsSending => true;
+        public override bool? IsSending => true;
 
         /// <inheritdoc />
         public MatchDirectlySendController(ICollection<(int, int)>[] keyMatches,
diff --git a/Modbus.Net/Modbus.Net/Interface/IController.cs b/Modbus.Net/Modbus.Net/Interface/IController.cs
index 2cb9431..c3fd62e 100644
--- a/Modbus.Net/Modbus.Net/Interface/IController.cs
+++ b/Modbus.Net/Modbus.Net/Interface/IController.cs
@@ -10,7 +10,7 @@ namespace Modbus.Net
         /// <summary>
         ///     消息维护线程是否在运行
         /// </summary>
-        bool IsSending { get; }
+        bool? IsSending { get; }
 
         /// <summary>
         ///     增加信息