Abstract: The longitudinal-vibration mathematical model of the Hybrid Longitudinal-Torsional Ultrasonic Motor is founded.And all kinds of the longitudinal-vibration process of the motor are derived by simulation.It is concluded that proper values of the preload and fiction material parameters must be choosed to get proper contact angle and the same-frequency of the longitudinal and Torsional vibrations for the steady output and high efficiency of the motor. Additionally,the rationality of the assumption of the force transfer model that the rotor is unmovable is verified.