The motion characteristics of linear ultrasonic motor based on inplane vibration were studied. The working principle of the motor and the conditions of the elliptical motion of the stator were briefly described. The contact state between the mover and the stator at the operation of the motor was analyzed. Combined with the periodic stretching vibration of the stator, the velocity variation trend of the mover in a period of the excitation signal was studied by takingthe equalvelocity point (the moment at which the speeds of the stator and the mover are the same) the critical contact point as the segmentation point. Thevelocity model and displacement model of the mover at the steady state were established. Based on the established model, the relationship between the assembly clearance of mover and stator and the velocity of the stator was studied by means of simulation.The results showed that, on the premise of ensuring the normal operation of the motor, there was an approximate linear relationship between the motion speed of the mover and the assembly clearance between the mover and the stator.