Abstract: A standing wave ultrasonic motor driven by using piezoelectric ceramic elements is studied experimentally and theoretically in this paper. In this motor, a longitudinal-torsion (L-T) coupler with improving construction was proposed, and vibration modes of L-T coupler were analyzed by using finite element method (FEM); The frequency equation of driving stator was derived from electromechanical equivalent network. With the improvement of coupler of this motor, the rotational speed of the motor with diameter of Φ32 mm is increased to 430 r.p.m with no load, that is as 3~4 times as the original one, and the maximum torque out and efficiency of the motor are 6 kgf.cm and 17% respectively.