Abstract: The excellent performance of proton exchange membrane fuel cells (PEMFCs) makes them suitable for applications including power generation, transportation, and aerospace. However, problems such as insufficient reliability and poor durability have severely restricted its industrialization process. Therefore, it is necessary to develop fault diagnosis methods to further improve fuel cell performance. This review paper first demonstrates the PEMFC system topology and its classical faults, and then summarizes the current research progress of PEMFC fault diagnosis methods including model-based, data-driven, experimental test based, and fusion method. Meanwhile, the current research status of PEMFC system online fault diagnosis is discussed. At last, the paper gives the potential developing tendency of the fault diagnosis in the future. Overall, the paper aims to contribute to the research and massive applications of the PEMFC.