After distribution network failure, a large number of alarm information will be generated. These information can be used to identify the faulty components quickly, and hence providing important decision support for dispatching center staff. Since the existing fault diagnosis methods of Petri nets are not applied in the distribution network, an improved hierarchical fuzzy Petri nets fault diagnosis method based on temporal constraints is proposed. An improved hierarchical fuzzy Petri net model for suspected fault component in distribution network is established, which can adapt to the change of network topology. The obtained alarm information is used to check the sequence of protection and circuit breakers by reverse and forward temporal reasoning, and the confidence of the transitions that does not meet the time constraints is corrected. The reasoning process and the matrix reasoning algorithm of the improved hierarchical fuzzy Petri net model are given. In the process of matrix reasoning, the modified probability of Gauss function is introduced to keep the probability at 0~1. Finally, the confidence probability of the fault components and its temporal point constraint are obtained. Through the comparison and analysis of the distribution network system examples, the correctness and rationality of the proposed method are verified, and the fault components of the distribution network can be effectively diagnosed.