Display system and method for automatic adjusting brightness

The invention provides a display system and method for automatic adjusting brightness. The display system comprises a display device, a desk lamp, a first photodetector, a second photodetector, and a controller. The controller adjusts an illumination parameter of the desk lamp according to an environmental light parameter detected by the first photodetector, and then adjust a display parameter of a screen in the display device according to a display device overall brightness detected by the second photodetector. Therefore, display quality is maintained and viewing comfort is improved.