diff --git a/Providers/FreeSql.Provider.MySql/MySqlCodeFirst.cs b/Providers/FreeSql.Provider.MySql/MySqlCodeFirst.cs
index e8c38cb0..b7aa46a0 100644
--- a/Providers/FreeSql.Provider.MySql/MySqlCodeFirst.cs
+++ b/Providers/FreeSql.Provider.MySql/MySqlCodeFirst.cs
@@ -240,7 +240,7 @@ where a.table_schema in ({0}) and a.table_name in ({1})", tboldname ?? tbname);
                             }
                             //添加列
                             sbalter.Append("ALTER TABLE ").Append(_commonUtils.QuoteSqlName($"{tbname[0]}.{tbname[1]}")).Append(" ADD ").Append(_commonUtils.QuoteSqlName(tbcol.Attribute.Name)).Append(" ").Append(tbcol.Attribute.DbType);
-                            if (tbcol.Attribute.IsNullable == false) sbalter.Append(" DEFAULT ").Append(_commonUtils.FormatSql("{0}", tbcol.Attribute.DbDefautValue));
+                            if (tbcol.Attribute.IsNullable == false && tbcol.Attribute.IsIdentity == false) sbalter.Append(" DEFAULT ").Append(_commonUtils.FormatSql("{0}", tbcol.Attribute.DbDefautValue));
                             if (string.IsNullOrEmpty(tbcol.Comment) == false) sbalter.Append(" COMMENT ").Append(_commonUtils.FormatSql("{0}", tbcol.Comment ?? ""));
                             if (isIdentityChanged) sbalter.Append(" AUTO_INCREMENT").Append(existsPrimary == null ? "" : ", DROP PRIMARY KEY").Append(", ADD PRIMARY KEY(").Append(_commonUtils.QuoteSqlName(tbcol.Attribute.Name)).Append(")");
                             sbalter.Append(";\r\n");
diff --git a/Providers/FreeSql.Provider.Odbc/MySql/OdbcMySqlCodeFirst.cs b/Providers/FreeSql.Provider.Odbc/MySql/OdbcMySqlCodeFirst.cs
index 1aeff28f..b1f9b8c2 100644
--- a/Providers/FreeSql.Provider.Odbc/MySql/OdbcMySqlCodeFirst.cs
+++ b/Providers/FreeSql.Provider.Odbc/MySql/OdbcMySqlCodeFirst.cs
@@ -228,7 +228,7 @@ where a.table_schema in ({0}) and a.table_name in ({1})", tboldname ?? tbname);
                             }
                             //添加列
                             sbalter.Append("ALTER TABLE ").Append(_commonUtils.QuoteSqlName($"{tbname[0]}.{tbname[1]}")).Append(" ADD ").Append(_commonUtils.QuoteSqlName(tbcol.Attribute.Name)).Append(" ").Append(tbcol.Attribute.DbType);
-                            if (tbcol.Attribute.IsNullable == false) sbalter.Append(" DEFAULT ").Append(_commonUtils.FormatSql("{0}", tbcol.Attribute.DbDefautValue));
+                            if (tbcol.Attribute.IsNullable == false && tbcol.Attribute.IsIdentity == false) sbalter.Append(" DEFAULT ").Append(_commonUtils.FormatSql("{0}", tbcol.Attribute.DbDefautValue));
                             if (string.IsNullOrEmpty(tbcol.Comment) == false) sbalter.Append(" COMMENT ").Append(_commonUtils.FormatSql("{0}", tbcol.Comment ?? ""));
                             if (isIdentityChanged) sbalter.Append(" AUTO_INCREMENT").Append(existsPrimary == null ? "" : ", DROP PRIMARY KEY").Append(", ADD PRIMARY KEY(").Append(_commonUtils.QuoteSqlName(tbcol.Attribute.Name)).Append(")");
                             sbalter.Append(";\r\n");
diff --git a/Providers/FreeSql.Provider.Odbc/SqlServer/OdbcSqlServerCodeFirst.cs b/Providers/FreeSql.Provider.Odbc/SqlServer/OdbcSqlServerCodeFirst.cs
index 20416a9b..f9448e14 100644
--- a/Providers/FreeSql.Provider.Odbc/SqlServer/OdbcSqlServerCodeFirst.cs
+++ b/Providers/FreeSql.Provider.Odbc/SqlServer/OdbcSqlServerCodeFirst.cs
@@ -276,7 +276,7 @@ use " + database, tboldname ?? tbname);
                             //添加列
                             sbalter.Append("ALTER TABLE ").Append(_commonUtils.QuoteSqlName($"{tbname[0]}.{tbname[1]}.{tbname[2]}")).Append(" ADD ").Append(_commonUtils.QuoteSqlName(tbcol.Attribute.Name)).Append(" ").Append(tbcol.Attribute.DbType);
                             if (tbcol.Attribute.IsIdentity == true && tbcol.Attribute.DbType.IndexOf("identity", StringComparison.CurrentCultureIgnoreCase) == -1) sbalter.Append(" identity(1,1)");
-                            if (tbcol.Attribute.IsNullable == false)
+                            if (tbcol.Attribute.IsNullable == false && tbcol.Attribute.IsIdentity == false)
                             {
                                 var addcoldbdefault = tbcol.Attribute.DbDefautValue;
                                 if (addcoldbdefault != null) sbalter.Append(_commonUtils.FormatSql(" default({0})", addcoldbdefault));
diff --git a/Providers/FreeSql.Provider.SqlServer/SqlServerCodeFirst.cs b/Providers/FreeSql.Provider.SqlServer/SqlServerCodeFirst.cs
index d786528b..e9249c2b 100644
--- a/Providers/FreeSql.Provider.SqlServer/SqlServerCodeFirst.cs
+++ b/Providers/FreeSql.Provider.SqlServer/SqlServerCodeFirst.cs
@@ -279,7 +279,7 @@ use " + database, tboldname ?? tbname);
                             //添加列
                             sbalter.Append("ALTER TABLE ").Append(_commonUtils.QuoteSqlName($"{tbname[0]}.{tbname[1]}.{tbname[2]}")).Append(" ADD ").Append(_commonUtils.QuoteSqlName(tbcol.Attribute.Name)).Append(" ").Append(tbcol.Attribute.DbType);
                             if (tbcol.Attribute.IsIdentity == true && tbcol.Attribute.DbType.IndexOf("identity", StringComparison.CurrentCultureIgnoreCase) == -1) sbalter.Append(" identity(1,1)");
-                            if (tbcol.Attribute.IsNullable == false)
+                            if (tbcol.Attribute.IsNullable == false && tbcol.Attribute.IsIdentity == false)
                             {
                                 var addcoldbdefault = tbcol.Attribute.DbDefautValue;
                                 if (addcoldbdefault != null) sbalter.Append(_commonUtils.FormatSql(" default({0})", addcoldbdefault));