A flat display and backlight module thereof are disclosed. The flat display includes a backlight module disposed on a rear surface of a display panel. The backlight module comprises lamps, a reflector, and a diffuser disposed on a back bezel. The reflector is attached on the back bezel. The diffuser and reflector form an enclosed space for the lamps, providing required light for the display panel. The back bezel comprises at least one outer surface with a plurality of fins extending therefrom to increase effective dissipation area thereof.