Abstract: This paper proposes a composite nonlinear control strategy that combines a nonlinear disturbance observer and an adaptive sliding mode controller for a multilevel Boost converter with a constant power load. First,exact feedback linearization method is used to transform the model into Brunovsky’s canonical form. Then under the premise of ensuring the large signal stability of the system,the adaptive control method and the nonlinear disturbance observer are added to the design of the sliding mode controller,and the stability of the entire closed-loop system is proved by Lyapunov theory. Simulation and experimental results show that,compared with the dual closed-loop PI control method,this control strategy has better dynamic regulation performance and stronger robustness.