An air system for a proton exchange membrane fuel cell belongs to the technical field of new energy automobiles, and is characterized in that an exhaust recirculating loop is used to lead the gas exhausted from a cathode outlet of a galvanic pile into an inlet loop of the galvanic pile again. According to the invention, the total flow, total pressure and oxygen flow entering into the galvanic pile can be adjusted independently, and the water logging or membrane drying of the galvanic pile can be effectively avoided while the monolithic voltage of the galvanic pile is limited; during the shutdown period, liquid water inside the galvanic pile can be dried quickly, so as to prevent the galvanic pile from being damaged caused by freezing of water residual inside the galvanic pile under the condition of low temperature; during the shutdown period, the whole pipeline can be filled with nitrogen, so as to prevent oxygen from entering into the anode to corrode the galvanic pile with long-term shutdown; and the fresh air amount entering into the system is reduced, and the load of the mechanical and chemical filter is reduced. The measures can effectively improve the service life and the durability of the fuel cell, and meanwhile, as the radiating and humidifying by-pass governing is led in, the machine warming speed of the galvanic pile under the condition of low temperature can be increased.