A backlight module includes a plurality of light sources, a photo-sensor, and a control circuit. Each light source of the plurality of light sources can operate independently. The photo-sensor detects the luminance of the plurality of light sources to generate a luminance signal. The control circuit drives the plurality of light sources according to the luminance signal. When the backlight module is used in a scanning backlight LCD, the control circuit turns off parts of the plurality of light sources according to a display signal. When all of the plurality of light sources is turned on, the control circuit obtains the luminance signal so as to adjust the luminance of the backlight module according to the luminance signal.