The utility model relates to a voltage reducing and starting resistance protector for the air compressor of internal combustion engine locomotive, comprising a power supply voltage stabilizing circuit, a fault delay circuit, an executive control circuit, an electro-optic coupling signal pick-up circuit, a fault display circuit, an anti-surge voltage circuit, and an unlocking button. The seven parts are connected in parallel at both ends of a voltage reducing and starting resistance. When the resistance can not shortly connect after three seconds, in the rating time, the power supply is automatically cut off, so as to prevent the occurrence of the fire disaster. The utility model has the advantages of reasonable design, security, and low cost. Through the experimental certification for long running, the utility model completely reaches the design requirements.