Aiming at the current situation of maintenance of integrated electrical system for certain type of self-propelled gun and based on the analysis of the structure, principles and characteristics of electrical system, the thesis is to develop faulty diagnosis expert system by adopting Fault Tree Analysis (FTA). Introduce the structure of faulty diagnosis expert system, to master basic theory by studying the structure of electrical system and failure mechanism, and to build knowledge base by collecting diagnostic knowledge from the experts. Develop integrated electrical system fault diagnosis expert system through forward reasoning mechanism. The results indicate that the method can improve the maintenance of electrical system and help maintainers complete complicated maintaining task in a shorter period.