chrislao您好：
使用TclientDataSet的CreateDataSet方法创建,试试看
procedure TForm1.Button1Click(Sender: TObject);
begin
 with clientDataSet1 do
   begin
     with FieldDefs.AddFieldDef do
       begin
         //添加一字段AAA
         DataType:=ftString;
         Name:='AAA';
         Size:='10';
       end;
     with FieldDefs.AddFieldDef do
       begin
         //添加一字段BBB
         DataType:=ftInteger;
         Name:='BBB';
       end;
     CreateDataSet;
   end;
end;