A multi-lamp driving system includes a power stage circuit, a pulse width modulation (PWM) controller, a plurality of transformer circuits, and an abnormal detection circuit. Each of the transformer circuits includes a first primary winding and a second primary winding connected in series and a first secondary winding and a second secondary winding respectively outputting AC power signals to drive at least one lamp. The abnormal detection circuit is connected to a junction of the first primary winding and the second primary winding of each of the transformer circuits, and determines if voltages of the junction of the first primary winding and the second primary winding of each of the transformer circuits are different to determine if the at least two lamps are normal. The abnormal detection circuit further generate control signals to control the PWM controller upon the condition that one of the at least two lamps are abnormal.