According to the stator work mechanism of linear ultrasonic motor, the difference of the two modal frequencies affects the output performance and efficiency of the motor. In order to solve the problem, the dynamic equation of the stator is solved with the structural perturbation theory. Then, the appropriate position for modifying the stator working modal frequencies into coincidence is obtained by the FEM analysis, as well as the relationship between the modification and difference of the two modal frequencies is given. Aimed at a samplestator, the difference of the two modal frequencies of the stator is changed from 400 Hz into 82 Hz by the method. The result shows that the method is convenient and feasible for adjusting two modal frequencies of Four-legged linear stator into coincidence.