With the development of the power electronics industry, switching power supply play an increasingly important role in the electronics industry, which has been widely applied to various fields of aviation, communications, transportation, etc. This paper conducts the design and research based on the DSP digital switching power supply. In terms of the principle, it makes the specific introduction on the work process of the fly-back converter and establishes the small-signal linearized modeling. In hardware, combining with system indicators of design, the filtered rectifier circuits, fly-back main circuit and clamp protection circuit arc analyzed at length; and the selecting principles are identified. In controller, the high performance TMS320F2812 is selected as controlling core. We design a DSP-based digital switching power supply with fully digital control and remote management and monitoring capabilities. It has greatly enhanced the intelligence, reduced the volume and influence of environment change.