It is the primary task for the reliable power supply and safe operation of the distribution network to make full use of the alarm information and time series information to quickly and accurately diagnose the faulty component after the fault of the distribution network. Based on the fault diagnosis of existing Petri nets, a fault diagnosis model for distribution network based on time-constrained hierarchical fuzzy Petri nets is proposed. The model established in this paper has good adaptability to the topology change of distribution network, and the starting point of the event action of reason is obtained by using the main protection and main protection corresponding to the action time of the circuit breaker, and the Gaussian function is corrected. The comparison of the example shows that the method has strong accuracy and versatility, and can effectively diagnose the fault of the distribution network. This work is supported by National Natural Science Foundation of China (No. 61803233).