the failure rate of the tank auto-loader is high and the causes of failure are complicated. In order to shorten the fault diagnosis time of the auto-loader and improve the diagnostic accuracy, after analyzing the internal principle of the automatic loading machine and obtaining relevant expert experience, a perception-based Fault diagnosis method for fuzzy Petri nets. Combined with the specific construction of the automatic loader, the corresponding PFPN fault model is established. The fuzzy Petri net is used to represent the fault propagation process. The perceptron error back-transfer method is used to learn the limited expert experience and determine the weight of the trigger event in the Petri network. Through forward reasoning, accurate judgment of the failure of the automatic loader is realized. Reverse reasoning combined with the minimum cut level method reduces the scope of investigation and improves the efficiency of reasoning. By taking the Rotary ammunition loader as an example, the corresponding PFPN fault model is established. By comparing with the fault tree model diagnosis results and historical diagnostic data, the rationality and effectiveness of the fault analysis method are verified.The fault diagnosis of automatic loader is realized quickly and accurately.