The invention discloses a nitrogen system which comprises a buffer tank, a PSA nitrogen generation system and a liquid nitrogen vaporization system, wherein the PSA nitrogen generation system is connected in parallel with the liquid nitrogen vaporization system; the PSA nitrogen generation system comprises an air compressor, a PSA nitrogen generator and a supercharger which are sequentially communicated, and a nitrogen outlet of the supercharger is communicated with a nitrogen inlet of the air compressor; the liquid nitrogen vaporization system comprises a liquid nitrogen storage tank for storing liquid nitrogen and a liquid nitrogen vaporizer communicated with the liquid nitrogen storage tank, and a nitrogen outlet of the liquid nitrogen vaporizer is communicated with a nitrogen inlet of the buffer tank; a switching device is arranged among the nitrogen outlet of the supercharger, the nitrogen outlet of the liquid nitrogen vaporizer and the nitrogen inlet of the buffer tank; due to the switching device, the nitrogen inlet of the buffer tank can be only communicated with the nitrogen outlet of the supercharger or the nitrogen outlet of the liquid nitrogen vaporizer. The cost of nitrogen generation can be effectively reduced through the structure design of the nitrogen system.