diff --git a/src/CAD/IFox.CAD.Shared/ExtensionMethod/DwgMark.cs b/src/CAD/IFox.CAD.Shared/ExtensionMethod/DwgMark.cs
new file mode 100644
index 0000000000000000000000000000000000000000..c82ed2334538493681887bc0b32be479d45a218a
--- /dev/null
+++ b/src/CAD/IFox.CAD.Shared/ExtensionMethod/DwgMark.cs
@@ -0,0 +1,63 @@
+namespace IFoxCAD.Cad;
+/// <summary>
+/// 为dwg文件添加标记
+/// </summary>
+public static class DwgMark
+{
+
+    private const int FREESPACE = 0x15;
+    private const int FREESPACEDEFAULT = 0x00;
+    /// <summary>
+    /// 为dwg文件添加标识
+    /// </summary>
+    /// <param name="file">DWG文件</param>
+    /// <param name="bite">ASCII标识字节0X00~0X7F</param>
+    /// <exception cref="ArgumentException">非dwg文件会报错，给定bite超界限也报错</exception>
+    public static void AddMark(FileInfo file, int bite)
+    {
+        if (file.Extension.ToLower() != ".dwg")
+        {
+            throw new ArgumentException("必须是dwg文件！");
+        }
+        if (bite > 0x7F || bite < 0x00)
+        {
+            throw new ArgumentException("字符必须在ASCII范围！");
+        }
+        using BinaryWriter bw = new BinaryWriter(File.Open(file.FullName, FileMode.Open));
+        bw.BaseStream.Position = FREESPACE;//文件头第21个字节
+        bw.Write(bite); //写入数据，仅一个字节
+    }
+    /// <summary>
+    /// 将dwg文件标记恢复为默认值
+    /// </summary>
+    /// <param name="file">文件</param>
+    /// <exception cref="ArgumentException">非dwg文件会报错</exception>
+    public static void RemoveMark(FileInfo file)
+    {
+        if (file.Extension.ToLower() != ".dwg")
+        {
+            throw new ArgumentException("必须是dwg文件！");
+        }
+        using BinaryWriter bw = new BinaryWriter(File.Open(file.FullName, FileMode.Open));
+        bw.BaseStream.Position = FREESPACE;//文件头第21个字节
+        bw.Write(FREESPACEDEFAULT); //写入数据，仅一个字节
+    }
+    /// <summary>
+    /// 获取设置的dwg文件标记
+    /// </summary>
+    /// <param name="file">文件</param>
+    /// <returns></returns>
+    /// <exception cref="ArgumentException">非dwg文件会报错</exception>
+    public static int GetMark(FileInfo file)
+    {
+        if (file.Extension.ToLower() != ".dwg")
+        {
+            throw new ArgumentException("必须是dwg文件！");
+        }
+        using FileStream fs = File.OpenRead(file.FullName);
+        fs.Seek(FREESPACE, SeekOrigin.Begin);
+        byte[] mark = new byte[1];
+        fs.Read(mark, 0, mark.Length);
+        return mark[0];
+    }
+}
diff --git a/src/CAD/IFox.CAD.Shared/IFox.CAD.Shared.projitems b/src/CAD/IFox.CAD.Shared/IFox.CAD.Shared.projitems
index 13b7df2fab9bc27b4d9543cabe8484f13627972f..c77cbc0db6addd99b35ac4e60c115857dd46af3c 100644
--- a/src/CAD/IFox.CAD.Shared/IFox.CAD.Shared.projitems
+++ b/src/CAD/IFox.CAD.Shared/IFox.CAD.Shared.projitems
@@ -28,6 +28,7 @@
     <Compile Include="$(MSBuildThisFileDirectory)ExtensionMethod\DBDictionaryEx.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)ExtensionMethod\DBObjectEx.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)ExtensionMethod\DBTransEx.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)ExtensionMethod\DwgMark.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)ExtensionMethod\EditorEx.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)ExtensionMethod\Entity\EntityBoundingInfo.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)ExtensionMethod\Entity\ArcEx.cs" />
diff --git a/tests/TestShared/TestDwgMark.cs b/tests/TestShared/TestDwgMark.cs
new file mode 100644
index 0000000000000000000000000000000000000000..cf0d712a10b0a146bf02f9985329a7b2ad7eb4b4
--- /dev/null
+++ b/tests/TestShared/TestDwgMark.cs
@@ -0,0 +1,11 @@
+namespace Test;
+using IFoxCAD.Cad;
+public class TestDwgMark {
+    [CommandMethod(nameof(DwgMarktest))]
+    public void DwgMarktest() {
+        FileInfo file = new FileInfo(@"D:\TEST\1.dwg");
+        DwgMark.AddMark(file, 0x4D);
+        DwgMark.RemoveMark(file);
+        int A = DwgMark.GetMark(file);
+    }
+}
\ No newline at end of file
diff --git a/tests/TestShared/TestShared.projitems b/tests/TestShared/TestShared.projitems
index 105f637098c07b1bd5b0043e9c63a50d34b41c03..dd9a61c7bf09dd35163d36749f6f014550dc3f2c 100644
--- a/tests/TestShared/TestShared.projitems
+++ b/tests/TestShared/TestShared.projitems
@@ -19,6 +19,7 @@
     <Compile Include="$(MSBuildThisFileDirectory)TestDBobject.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)TestDBTrans.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)TestDwgFilerEx.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)TestDwgMark.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)TestEditor.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)TestEnv.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)TestExtents.cs" />