With the development of power electronic technology, the control technology of power electronic device is becoming more and more complicated. The switching power supply is a indispensable component in modern power electronic equipment. Its quality and size have a direct impact on the whole performance of electronic equipment. Digital control technology and the applications of FPGA have become a new research hotspot in the field of power electronics. Digital control can reduce the aging of the device and the impact of temperature drift on the accuracy of the convenient. This paper studies the digital switching power supply based on FPGA and points out the system structure of the system.