In the study of three level inverter, due to the unbalance of neutral-point-voltage, resulting in the output waveform distortion, which made the inverter can not meet the operational requirements. For this, the diode clamped three level inverter causes neutral-point-voltage unbalance is analyzed in this paper, and a control strategy based on the Buck-Boost balance circuit is presented, which is verified by Matlab/Simulink. The simulation results show that the control strategy presented in this paper for the Buck-Boost balance circuit, can effectively suppress the unbalance of neutral-point-voltage, and the effect of conditions in some way better than small vector adjustment by SVPWM.