Abstract: This paper studies on a linear ultrasonic motor based on the vibration in plane of the rectangular plate. First, the structure of the thin rectangular piezoelectric ceramic plate (the key part of this kind of motor) has been theoretically designed and a conclusion that the practical ratio of the length to the width of this thin rectangular plate is 4.0 is drawn, and some corresponding analysis and validation are done by the ANSYS package. Then, the excitation of the working vibration modes and the working principle of this kind of motor have been relatively deeply analyzed and discussed for the first time. At last, the experimental results show that the error is only 3.74%, therefore the correctness of the relevant analysis in this paper is obtained.