Abstract: The reliable operation of the power supply system is of great significance to the long-term efficient operation of the entire large accelerator. The N+1 modular self-balanced parallel redundant power supply can significantly improve the reliability of the power supply system under the currently executable power supply technology. The research and reliability analysis of the magnet power supply for this structure were carried out, and the reliability of the power supply was estimated in this paper. The result shows that the MTTR of the power supply is one-third less than that of a single module in one year, and the MTTR of the power supply is less than 1/2 of a single module MTTR in the first half of the year. The failure rate of N+1 modular self-balanced parallel redundant power supply shows the feature of low in early stage and high in late stage. This kind of power supply has greater advantage in reliability when the reliability of the power supply is high, and is an ideal choice for an accelerator power supply.