用这个方法也可以
 在interface的private里加入
 
PROCEDURE CMEraseBkgnd(var Message:TWMEraseBkgnd);Message WM_ERASEBKGND;
 
在implemetation里加入
 PROCEDURE Tform1.CMEraseBkgnd(var Message:TWMEraseBkgnd);
 BEGIN
   brush.style:=bsClear;
   Inherited;
 END;


procedure TForm1.FormCreate(Sender: TObject);
 begin
   BorderStyle := bsNone;
   Brush.Style := bsClear;
 end;