NOVELTY - The system is included with control section and cathode exhaust gas re-circulating section. The control section is included with controller, vacuum pump and vacuum tank, electromagnetic valve, vacuum valve, control valves (2,4,5,7,8,15,16), temperature sensor, humidity sensor and pressure sensor. The cathode exhaust gas re-circulating section is included with mechanical and chemical filtering device (17), intake and exhaust circuit and exhaust gas recirculation loop. The condenser (12) and oxygen sensor (14) are connected in series.    USE - Cathode exhaust re-circulating system for proton exchange membrane fuel cell for energy source automobile.    ADVANTAGE - 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 limiting the monolithic voltage of the galvanic pile. The liquid water inside the galvanic pile can be dried quickly during the shutdown period, 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. The whole pipeline can be filled with nitrogen during the shutdown period, so as to prevent oxygen from entering into the anode to corrode the galvanic pile with long-term shutdown. The fresh air amount entering into the system can be reduced, and the load of the mechanical and chemical filter can be reduced. The measures can effectively improve the service life and the durability of the fuel cell. The machine warming speed of the galvanic pile under the condition of low temperature can be increased.    DETAILED DESCRIPTION - The system has air inlet passage that is included with sensor group (S1), air flow rate sensor, control valves, air compressor (3), radiator (6), humidifier (9) and electric stack air inlet. The radiator bypass circuit is provided with third control valve. The long term load operation is prevented by adjusting the control valves.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of the cathode exhaust re-circulating system. (Drawing includes non-English language text)    Control valves (2,4,5,7,8,15,16)    Air compressor (3)    Radiator (6)    Humidifier (9)    Condenser (12)    Oxygen sensor (14)    Mechanical and chemical filtering device (17)