Backlight brightness control method and system

The invention provides a backlight brightness control method and system. According to the backlight brightness control method, external environment brightness is acquired, and backlight brightness corresponding to the acquired external environment brightness is searched from a corresponding relationship curve graph of the external environment brightness and backlight brightness matched with the external environment brightness, and the current backlight brightness of a display device is adjusted to be consistent with the searched backlight brightness, and therefore, the brightness of the display device can be adjusted automatically according to the external environment brightness, and damage to the eyes of a user because the backlight brightness of the display device is too high or too low can be decreased. The method and system provided by the invention are particularly applicable to smart TVs which are display devices of which the screens are gazed by the user for a long time who neglects external environment changes easily.