Abstract: In this paper, the power circuit adopts the Buck synchronous rectification topology, selects the STM32F334 with peripherals such as float process unit, high-resolution PWM, high-speed ADC, high-speed comparator as the processor, and uses PID control algorithm to complete a digital power design. In case of big output error as a result of large load changes, the integral separation is used to optimize the PID algorithm in order to reduce the PID overshoot. In addition, the algorithm is optimized by selecting appropriate sampling points, setting appropriate dead time and other control methods. A set of solutions suitable for digital power system are proposed. Tests have verified that the power supply has high control accuracy, high efficiency, and good steady-state and dynamic performance.