Proton exchange membrane fuel cells (PEMFCs) are potential solutions for the dual problems of energy shortage and environmental pollution, due to their high efficiency, low temperature, and eco-friendliness. However, the slow kinetic process in its cathodic oxygen reduction reaction (ORR) has to rely on scarce and expensive Pt-based catalysts, which hinders the further development and application of PEMFC technology. In order to reduce the cost and ensure efficient catalytic performance, researchers have developed various technological strategies in recent years, and alloying with Pt through the introduction of transition metals is one of the main strategies, especially PtCo bimetallic catalysts, which exhibit superior ORR catalytic performance. This paper reviews the research results and current status of PtCo alloy catalysts for PEMFCs in recent years. Firstly, it summarizes the effects of modulation strategies such as catalyst component control, particle size modulation, crystal surface modulation, and doping on the catalytic activity of fuel cells. Then, it introduces the most promising PtCo alloy structures, such as polyhedral, core-shells, nano-frames, and ordered intermetallic structure, etc. It also discusses the research on catalyst supports. Finally, it identifies the existing challenges and future prospects of PtCo alloy catalysts for their applications.