Abstract: Gives a theoretical analysis to the characteristics of wave metion and the design of structural parameters for the stepping ultrasonic amplitude transformer,which has the function of amplifying the amplitude of vibration and wave coupling in ultrasonic motors.The result has become the basis of designing ultrasonic motor prototypes.Ih the meantime,the problem of matching the various parts in the design of ultrasonic motor's stator, stress concentration of ultrasonic amplitude transformer,and the choice of frictional materials are discussed.