The invention relates to an ultrasonic motor servo control system asymmetric hysteretic compensation control device and method. The device comprises a control system, a base and an ultrasonic motor which is arranged on the base. One side output shaft of the ultrasonic motor is connected with a photoelectric encoder, and the other side output shaft is connected with a flywheel inertial load. The output shaft of the flywheel inertial load is connected with a torque sensor through a coupler. The signal output ends of the photoelectric encoder and the torque sensor are connected with the control system. The control device comprises an asymmetric hysteretic compensation controller and the motor. The whole control method is established on the basis of the compensation controller, and the minimum identification error acts as the adjustment function on the aspect of design of the controller so that the better control efficiency can be acquired. According to the device and the control system thereof, the control accuracy is high, the structure is simple and compact and the use effect is great.