Thank you yrt, I tried your method.
I put "LCD_FillRect(0, 0, CHIP_SCREEN_WIDTH, CHIP_SCREEN_HEIGHT, RGB_WHITE);" under Application_Ini,and all the volume control button gone.
And I also find that in "Hardware-scrolling-1.0" example code,we need to add "LCD_FullScreen(1)" under Application_Handler,
if not the first few lines(at top) will not be displayed,
it seems without this function call,all lines draw to original toolbar area will be ignored.
by the way,my platform is Open4(stm32f107c),use latest os(Circle-OS-4.61).