A backlight driving system comprises an inverter module, a current balance module, a feedback module and an open-lamp protection detection module. The inverter module provides electrical signals to a plurality of lamps. The current balance module balances currents flowing through the plurality of lamps. The feedback module detects the current of the backlight and generates a feedback signal to the invert module accordingly. The open-lamp protection detection module detects voltage variations of the feedback transformer and generates a detection signal to the inverter module accordingly. The inverter module regulates the currents flowing through the plurality of lamps according to the feedback signal and determines one or more of the plurality of lamps are faulty according to the detection signal generated by the open-lamp protection detection module, and stops providing the electrical signals to the plurality of lamps.