High Intensity heavy ion Accelerator Facility (HIAF) aims to provide heavy ion beams with the highest pulse beam intensity in the world, and BRing (Booster Ring) is its main accelerator. Therefore, the HIAF-BRing dipole magnet pulse power supply needs to output fast, high-precision large current and wide range of high voltage. Not only that, the power supply also needs to meet the requirement of long-term stable operation. These requirements mean that the structure and reliability design of power supply are very important. In order to meet these requirements, project team proposes a variable-voltage fast-cycling energy storage pulse power supply and develops a prototype. This paper focuses on the structure and reliability design of power supply. In terms of structure and reliability design, the characteristics of power supply are fully considered and combined. Especially for the H-bridge IGBT, use the FLOTHERM software to perform thermal simulation according to the actual working conditions to obtain important data and optimize the design. The experiment of working principle verified the working principle of power supply, and the feasibility of the structure and reliability design was verified through the 72-hour reliability experiment.