Impedance characteristic contains important electrical parameters of the ultrasonic motor driving system. Large working current causes the ultrasonic motor (USM) to heat fast, decrease stability and reduce the efficiency of drive system. The impedance characteristic of the system usually affects the working current of the circuit. Currently, the tests of the impedance characteristic of the USM and its driving system are only carried out on a single stator and under low voltage. In this paper, the parallel equivalent circuit model of the USM and its driving system is proposed to obtain the impedance characteristics of the electromechanical system by simulation, and the practical impedance characteristics of the USM are obtained by processing the electric signals through the Fourier decomposition method. The results reveal how the system′s impedance changes with the other parameters. It monotonously increases when the driving frequency decreases; it is reduced when the load torque increases (less than the locked rotor torque). The smaller the resonant matching frequency of electromechanical system, the smaller the system impedance is; the closer the resonance frequency to the resonant frequency of the resonant frequency, the faster the system′s impedance mode increases with the decrease of the driving frequency. Finally, it is summarized that the ideal working frequency of the USM and the matching resonant frequency of the driving circuit should both be slightly larger than the resonant frequency of USM according to the mechanical and electrical impedance characteristics.