Abstract: In order to improve product reliability, and to quickly identify the source of failure when the electronic equipment breaks down, thus to protect normal operation of the equipment, this paper introduces the diagnosis modeling method based on the multi-signal flow model, and then develops the multi-signal flow fault diagnosis strategy, which is based on the important prior knowledge of the fault, thus improves the technique of multi-signal flow diagnosis by introducing failure probability of the fault mode. The method is then applied to BEPCⅡ magnet power interface control equipment fault diagnosis system by using TEAMS toolbox modeling, which realizes rapid and accurate fault diagnosis and positioning, improves the diagnosis ability of magnet power control equipment, and can be easily extended to other devices and systems.