This study proposed a method that using membership function and neural network for motor diagnosis. The relationship between faults and frequency symptoms built up by expert experiences and overhaul information for motors. Using this relationship to diagnosing by the similarity method and training with the neural network. The frequency symptoms extracted by measured signals and graduated by membership function, and diagnosis by the neural network. In this paper, diagnosis by using fuzzy neural network in two cases and compared with similarity method and neural network to prove the detect ability of the neural network for multiple faults.