thank you for your advice but i further explore and i think my video card is ok.but the screen have problem because after i clone the display with other desktop screen it works fine. Is there any means rather than changing screen?
It would seem that you do need to change the screen. your testing another display proves that there is nothing wrong with the hardware so nothing to fix.
You issue could be the screen or a connection to the screen, either way unless you are comfortable taking it apart yourself it looks like a job for a repair centre.