Abstract: In high power occasions such as traction driving system of AC electrical locomotive, due to the limitation of switching frequency, voltage or current harmonic, optimized PWM strategy is often used, in which current harmonic minimum PWM（CHMPWM） is considered in especial due to its excellent harmonic performance of output voltage and current. It can reduce the current harmonic obviously, thus has great advantage in the improvement of motor control performance and system efficiency. In this paper, the switching angles curves of CHMPWM with respect to modulation ratio are calculated first. Secondly, taking induction machine as the load, the current harmonic performance is studied through the calculation of weighted total harmonic distortion（WTHD） and current harmonic amplitude. The results are compared with those of selected harmonic elimination PWM（SHEPWM）. And then, the torque pulsation under CHMPWM is analyzed in theory. Simulation and experimental results proved the validity of the theory analysis.