The present disclosure provides a testing apparatus of an auxiliary belt system. The testing apparatus of the auxiliary belt system includes: a tester bracket, a torque pulse simulation motor mounted to the tester bracket, a crankshaft pulley mounted to the tester bracket and rotated by operations of the torque pulse simulation motor, an auxiliary system mounted to the tester bracket, connected to the crankshaft pulley through a belt and rotated by rotation of the crankshaft pulley and a controller controlling operations of the torque pulse simulation motor.