The disclosure provides an apparatus for controlling liquid crystal display brightness, the apparatus pre-obtaining a zone backlight value corresponding to a zone image data block according to grayscale values; if the zone backlight value is above a first threshold, multiplying the pre-obtained zone backlight value with a backlight value gain coefficient, which is more than 1, to a obtain backlight value to which a gain is applied, of a backlight zone corresponding to the zone image data block, outputting the backlight value to which the gain is applied, to a driver circuit of backlight source in the backlight zone to control brightness of the backlight source in the backlight zone as a result of driving; if the zone backlight value is below a second threshold, compensating for the grayscale values of the pixels in the zone image data block using compensation coefficients, each of which is more than 1.