Abstract: Multilevel rectifiers have broad application scenarios in high voltage and high power applications. In this paper, the three-phase five-level rectifier with coupled inductor was studied. The first step was to analyze the working principle of the three-phase five-level rectifier and established a mathematical model. Secondly, in view of the problem of steady-state error when traditional sliding mode control was applied to the rectifier, a nonlinear integral sliding mode control strategy fused with proportional integral was proposed, which realized the differential tracking of the output voltage of the rectifier. And the Lyapunov function was used to verify the stability of the integral sliding mode control of the designed rectifier. Finally, the negative-sequence voltage injection method was adopted to solve the inherent output voltage imbalance problem of the rectifier with multiple DC outputs, and the proposed control method was simulated and tested to verify its correctness and effectiveness.