This paper presents a calculation method of parameters of high frequency equivalent circuits of inverter-driven permanent magnet synchronous motors (PMSM). The high frequency oscillatory current such as leakage current to the motor frame (common-mode current) and high frequency oscillatory line current (normal-mode current), are caused due to switching of inverter transistors. A parameter search method based on the particle swarm optimization algorithm is proposed. Agents in the algorithm are grouped so that convergence performance is improved. Some simulation results illustrate the effectiveness of the proposed algorithm.