procedure TForm1.Timer1Timer(Sender: TObject);
var
m:tmessage;
begin
m.Msg:=WM_VSCROLL;
m.WParamLo:=SB_LINEDOWN;
m.WParamHi:=1 ;
m.LParam:=0;
postmessage(self.DBGrid1.Handle,m.Msg,m.WParam,m.LParam);

end;

procedure TForm1.Button1Click(Sender: TObject);
begin
self.Timer1.Enabled:=true;
end;

如果需要让他自动不断地从头到尾滚动，添加如下代码
if table1.Eof then table1.First;