Aiming at the nonlinear characteristics of high-order voltage-controlled converters, a sliding mode control method to suppress the chaos in the DCM-mode SEPIC converter is proposed. The method first improves the selection of state variables according to the working mode characteristics of the DCM mode SEPIC converter, so that the corresponding phase trajectories can enter the sliding surface in the DCM mode, and select the corresponding sliding mode function according to the existence conditions of the sliding mode function. Sliding mode coefficient. Then the adaptive hysteresis control is introduced. By setting the upper and lower limits of the hysteresis, the purpose of stabilizing the switching frequency is achieved. Finally realized the chaos control of the system. The simulation results of the method by building the Simulink model of the system show that the method can make the system run stably in a single-period state even in the case of large disturbances in the system, and has the characteristics of fast dynamic response and small output ripple.