The present invention discloses a backlight driving circuit applied to an electronic device. The backlight driving circuit includes a light-emitting diode unit, a photosensitive element, and a control circuit. The light-emitting diode unit has an anode terminal and a cathode terminal. The photosensitive element is coupled between the cathode terminal of the light-emitting diode unit and a ground, wherein the resistance of the photosensitive element changes with the ambient light level around the electronic device. The control circuit includes a sensing terminal and an output terminal. The sensing terminal receives a feedback voltage. The output terminal provides a power source to the anode terminal of the light-emitting diode unit according to the feedback voltage to control the luminance of the light-emitting diode unit, wherein the feedback voltage is decided by the resistance of the photosensitive element.