The invention provides a new energy automobile centralized gas supply system and gas supply method. The gas supply method comprises the following steps that after air is filtered through an air filter, the air enters a two-grade compressed air compressor to be compressed and boosted, and one-grade compressed air is led into a fuel cell system to conduct reaction and generate power through a by-pass valve; the one-grade compressed air passing the fuel cell system enters an air expander to recycle part of power; after two-grade compressed air exhausted from the two-grade compressed air compressor enter an air cooling heat exchanger to be cooled, most of the two-grade compressed air is supplied to an automotive breaking system, and the rest part of the two-grade compressed air is supplied to an air expanding refrigerator to be used for in-vehicle refrigeration in summer; and hot air exhausted from the air cooling heat exchanger can enter into an automobile to conduct heating in winter. According to the gas supply method, an electric refrigeration and heating system is not needed, energy is centrally supplied to the fuel cell system, the automotive breaking system and a in-vehicle refrigeration and heating module mainly by using one two-grade compressed air compressor, loss caused by energy conversion is reduced, the power consumption efficiency of the new energy automobile is improved greatly, and the driving distance is prolonged.