The fault detection of tolerance analog circuit is very important for the stable operation of electronic equipment. In view of the shortage of large calculation cost, long training time and high error rate, the fault detection algorithm of tolerance analog circuit based on modular neural network is proposed. The function modules of the neural network detection model are divided, and the fault signal features of the tolerance analog circuit are extracted based on the functional modules, and the Euclidean distance based on the sample center to the fault feature point is compared with the feature vectors of the fault samples, and the fault tolerance analog circuit fault is realized by the modular neural network decision classification function. Accurate location and detection. The simulation data show that the detection algorithm has advantages under the condition of different sample capacity, and the minimum error is 0.382%.