In order to solve the problems of high total harmonic distortion rate of output voltage and unbalance of mid-point potential of three-level inverter controlled by traditional methods, a dynamic modulation wave adjustment method is designed. With diode clamping type three level inverter control method as the research object, the potential at the point of the operation in low frequency wave phenomenon is analyzed, through the neutral voltage offset balance operation real-time calculated, and the offset stack to the middle phase modulation wave into the upper and lower modulation wave, and the use of digital signal processing (DSP) as the main controller, and set up three level inverter circuit experiment validation. Experimental results show that the control effect of this method is ideal and the ac power quality can be improved.