The invention provides an air supply system and method for a proton exchange membrane fuel cell. One end of a purging branch is connected between an air inlet device and a humidifier; the other end ofthe purging branch is connected to a cavity of a proton exchange membrane fuel cell; a first flow regulating device is arranged on the purging branch; a motor controller is used for regulating the first flow regulating device when it is monitored that an air compressor has a surge phenomenon to control part of air to enter the cavity of the proton exchange membrane fuel cell through the first flow regulating device, the air entering the cavity of the proton exchange membrane fuel cell causes reduction of air entering a fuel cell stack, so that the rotating speed of an air compressor is required to be improved correspondingly to allow the air compressor to jump out a surge area, the jumping-out of the surge area means that the air compressor eliminates the surge phenomenon, and therefore,the problems that when the surge phenomenon happens to the air compressor, the air compressor is damaged, and the cycle service life of the air compressor is affected are solved.