Aimed at the problem that midpoint voltage is out of balance in threelevel active midpoint clamp inverter (ANPC), an improved SVPWM control strategy is proposed. Firstly, the reasons of the point voltage imbalance in the ANPC inverter are analyzed, the midpoint current formed by each vector is analyzed by the space vector synthesis method, and an improved modulation algorithm is proposed by using vector in large vector synthesis. The offset of midpoint voltage in SVPWM modulation mode is analyzed, and a solution is given. On the basis of this, the modified SVPWM control strategy and the traditional SVPWM control strategy are simulated and compared with others, and the advantages of the improved algorithm are analyzed. Finally, the results are verified by the experimental platform. The results show that the modified SVPWM control strategy can effectively balance with the midpoint voltage, and can correct offset to be the midpoint voltage in time, and can make the midpoint voltage weak in fluctuation.