Abstract: In this paper, the vibration theory of the vibrating plate about a mode conversion ultrasonic motor and the force of the end of the vibrating plate were analysed theoretically. We conclude the rmponse of the fiexural vibration to the transient frichonal force, and discuss the drift of the inherent frequency of the vibrating plate and relation between the width of the vibrating plate and the diameter of the rotator, etc.Finally, give out the method of designing the vibrating plate.