procedure TForm1.Button1Click(Sender: TObject);
begin
   SetCaption(button1,'第一行','第二行',form1.Color);
end;

procedure TForm1.SetCaption(AButton: TButton; ACaption1,
  ACaption2: string;color:TColor);
var
  dc:Hdc;
  info:tagsize;
begin
  AButton.Caption:='';
  dc:=GetDC(AButton.Handle);
  SetBKColor(dc,Color);
  SetBkMode(dc, TRANSPARENT);
  GetTextExtentPoint32(dc,pchar(ACaption1),length(ACaption1),info);
  Textout(dc,AButton.Width div 2-info.cx div 2,AButton.Height div 2-info.cy,pchar(ACaption1),length(ACaption1));
  GetTextExtentPoint32(dc,pchar(ACaption2),length(ACaption2),info);
  TextOut(dc,AButton.width div 2-info.cx div 2,AButton.Height div 2,pchar(ACaption2),length(ACaption2));
end;