The traditional sliding mode control has the problems of slow approach speed, large buffeting, slow response speed and low precision when applied to a synchronous Buck converter. A novel nonsingular terminal sliding mode control method is proposed. Firstly, the traditional sliding mode surface function is modified. By introducing a nonlinear function and attaching the integral term, the system can be forced to converge quickly, thus reducing the response time. Secondly, based on the traditional approach law, a function of the form sigmoid is introduced, and a saturation function is used to replace the sign function, which avoids the high-frequency switching of the sign function near zero, and thus reduces the chattering effect caused by the traditional sliding mode control. Finally, the corresponding model is built on the MATLAB/Simulink simulation platform, and the results show that the adjustment time is 90 μs and the recovery time after sudden loading is 20 μs. The experimental results show that when the speed instruction changes, the proposed method can adjust the time faster, and the anti-interference ability is stronger after sudden loading.