A backlight module for a display panel of a display device is provided. The backlight module comprises a light-emitting unit and a control unit. The light-emitting unit provides light to the display panel. When the display panel displays images in a first mode, the control unit drives the light-emitting unit to emit light of a first total brightness. When the display panel displays images in a second mode, the control unit drives the light-emitting unit to emit light of a second total brightness.