In this paper,a constant frequency non-singular terminal sliding mode control strategy is adopted to solve the problem of the complex average current control compensator of the BUCK converter design,the slow dynamic response speed and the problem of unfixed switching frequency in conventional sliding mode variable structure’s control.Based on the switch state of the converter,the state space equation of the system is established,the switching surface function is designed,and the non-singular terminal sliding mode control law is derived.Finally,the simulation analysis is carried out,the simulation results indicate that compared with the average current control,the overshoot of the output voltage in the non-singular terminal sliding mode control BUCK converter is reduced by more than 50% and the dynamic response time is greatly reduced when the input voltage and the output current step change of the system occurred.