The invention discloses a coal-mine liquid-nitrogen fire-prevention cooling system. The coal-mine liquid-nitrogen fire-prevention cooling system comprises a liquid-nitrogen tank car, wherein the liquid-nitrogen tank car is connected with a main liquid-nitrogen delivery pipe, the main liquid-nitrogen delivery pipe is connected with a main direct liquid-nitrogen injection pipe and a liquid-nitrogen gasifying and cooling device respectively, the main direct liquid-nitrogen injection pipe is used for injecting liquid nitrogen into a high-temperature oxidation area, the liquid-nitrogen gasifying and cooling device is used for gasifying liquid nitrogen into gaseous nitrogen, and a gaseous nitrogen pipe for filling the gaseous nitrogen into the high-temperature oxidation area is connected onto the liquid-nitrogen gasifying and cooling device. The invention further discloses a coal-mine liquid-nitrogen fire-prevention cooling method adopting the coal-mine liquid-nitrogen fire-prevention cooling system to perform fire-prevention cooling. The coal-mine liquid-nitrogen fire-prevention cooling method and the coal-mine liquid-nitrogen fire-prevention cooling system achieve dual fire extinguishment effects by integrating the two fire prevention and fire extinguishment modes of liquid-nitrogen injection and gaseous nitrogen injection.