diff --git a/src/JT808.Protocol.Extensions/JT808.Protocol.Extensions.SuBiao/MessageBody/JT808_0x9208.cs b/src/JT808.Protocol.Extensions/JT808.Protocol.Extensions.SuBiao/MessageBody/JT808_0x9208.cs
index ee22969..e1bb881 100644
--- a/src/JT808.Protocol.Extensions/JT808.Protocol.Extensions.SuBiao/MessageBody/JT808_0x9208.cs
+++ b/src/JT808.Protocol.Extensions/JT808.Protocol.Extensions.SuBiao/MessageBody/JT808_0x9208.cs
@@ -137,7 +137,7 @@ namespace JT808.Protocol.Extensions.SuBiao.MessageBody
             writer.WriteByte(value.AlarmIdentification.AttachCount);
             writer.WriteByte(value.AlarmIdentification.Retain);
             writer.WriteString(value.AlarmId.PadRight(32, '\0'));
-            writer.WriteArray(Retain);
+            writer.WriteArray(value.Retain);
         }
     }
 }
diff --git a/src/JT808.Protocol.Test/JT808SerializerTest.cs b/src/JT808.Protocol.Test/JT808SerializerTest.cs
index 09376c0..241ef48 100644
--- a/src/JT808.Protocol.Test/JT808SerializerTest.cs
+++ b/src/JT808.Protocol.Test/JT808SerializerTest.cs
@@ -52,7 +52,7 @@ namespace JT808.Protocol.Test
         {
             var config = new DefaultGlobalConfig("merge");
             config.EnableAutoMerge = true;
-            config.AutoMergeTimeoutSecond = 5;
+            config.AutoMergeTimeoutSecond = 500;
             var array = new[]
             {
                 //分包数据第一包
@@ -67,6 +67,7 @@ namespace JT808.Protocol.Test
                 var package = config.GetSerializer().Deserialize(array[i - 1].ToHexBytes());
                 if (i == array.Length)
                 {
+                    Assert.True(package.Header.MessageBodyProperty.IsMerged);
                     Assert.NotNull(package.Bodies);
                     //分包合并成功并获取消息体进行处理
                     if (package.Bodies is JT808_0x0104 _0x0104 && _0x0104.AnswerParamsCount > 0)
@@ -86,6 +87,7 @@ namespace JT808.Protocol.Test
                 var package = config.GetSerializer().Deserialize(array[i].ToHexBytes());
                 if (i == 0)
                 {
+                    Assert.True(package.Header.MessageBodyProperty.IsMerged);
                     Assert.NotNull(package.Bodies);
                     //分包合并成功并获取消息体进行处理
                     if (package.Bodies is JT808_0x0104 _0x0104 && _0x0104.AnswerParamsCount > 0)
diff --git a/src/JT808.Protocol/Internal/DefaultMerger.cs b/src/JT808.Protocol/Internal/DefaultMerger.cs
index eef59e7..d28099b 100644
--- a/src/JT808.Protocol/Internal/DefaultMerger.cs
+++ b/src/JT808.Protocol/Internal/DefaultMerger.cs
@@ -41,7 +41,6 @@ namespace JT808.Protocol.Internal
         /// <inheritdoc/>
         public bool TryMerge(JT808Header header, byte[] data, IJT808Config config, out JT808Bodies body)
         {
-            // TODO: 添加SplitPackages缓存超时，达到阈值时移除该项缓存
             body = null;
             var timeoutKey = GenerateKey(header.TerminalPhoneNo, header.MsgId);
             if (!CheckTimeout(timeoutKey)) return false;
@@ -65,6 +64,7 @@ namespace JT808.Protocol.Internal
                     if (config.MsgIdFactory.TryGetValue(header.MsgId, out var value) && value is JT808Bodies instance)
                     {
                         body = instance.DeserializeExt<JT808Bodies>(ref reader, config);
+                        header.MessageBodyProperty.IsMerged = true;
                         return true;
                     }
                 }
diff --git a/src/JT808.Protocol/JT808.Protocol.xml b/src/JT808.Protocol/JT808.Protocol.xml
index 268fdb7..af8e06e 100644
--- a/src/JT808.Protocol/JT808.Protocol.xml
+++ b/src/JT808.Protocol/JT808.Protocol.xml
@@ -6089,6 +6089,11 @@
              false-0 消息头中无消息包封装项字段。
             </summary>
         </member>
+        <member name="P:JT808.Protocol.JT808HeaderMessageBodyProperty.IsMerged">
+            <summary>
+            当<see cref="P:JT808.Protocol.JT808HeaderMessageBodyProperty.IsPackage"/>为true时，表示是否已自动合并为完整的包
+            </summary>
+        </member>
         <member name="P:JT808.Protocol.JT808HeaderMessageBodyProperty.Encrypt">
             <summary>
             加密标识，0为不加密
diff --git a/src/JT808.Protocol/JT808HeaderMessageBodyProperty.cs b/src/JT808.Protocol/JT808HeaderMessageBodyProperty.cs
index de35c38..556769d 100644
--- a/src/JT808.Protocol/JT808HeaderMessageBodyProperty.cs
+++ b/src/JT808.Protocol/JT808HeaderMessageBodyProperty.cs
@@ -91,6 +91,10 @@ namespace JT808.Protocol
         /// </summary>
         public bool IsPackage { get; set; } = false;
         /// <summary>
+        /// 当<see cref="IsPackage"/>为true时，表示是否已自动合并为完整的包
+        /// </summary>
+        public bool IsMerged { get; set; }
+        /// <summary>
         /// 加密标识，0为不加密
         /// 当此三位都为 0，表示消息体不加密；
         /// 当第 10 位为 1，表示消息体经过 RSA 算法加密；