After analyzing the characteristics of multiple fault modes,the case knowledge database is established for multiple faults,and a multiple fault diagnosis method for electric equipments based on the two-step case retrieval strategy is proposed.The weight membership is employed to generate the initial candidate cases,which reduces the number of candidate cases greatly.Subsequently,the most probable fault case is obtained through the calculation of case similarity with the grey relational analysis,which avoids the problem of time-consuming computation resulting from the combination explosion of multiple faults.Finally,an example is embedded in the description of the methodology for better understanding.