In the modular multilevel converter (MMC) fed permanent magnet synchronous motor (PMSM) drive system, the DC voltage ripples and output current harmonic will severely deteriorate the performance of PMSM. In this paper, a CPS-PWM strategy with optimal phase shift angle is presented for full-bridge MMC-PMSM system. Optimal phase shift angle calculating by double Fourier series analysis of output current can effectively improve the harmonic characteristics of MMC output current, without introducing any high frequency circulation. The ultimate goal is to enhance the performance of PMSM when it is operating at low speed. The validity of the proposed means has been verified by simulation results.