Abstract: This paper proposes a bi-directional linear ultrasonic motor. It has the features such as simple construction and control, flexible direction control, The performance parameters of the prototype:frequency 21.46 kHz, maximum moving speed 400 mm/s under pre-load 3.2 N, maximum thrust 2.1 N under pre-load 1.6 N. Several typical locus are obtained by using MATLAB simulation software. The influence of phase shift and vibration amplitude of ultrasonic transducers on ideal elliptical locus and output characteristics is investigated by using theoretical and experimental methods.