Abstract: The boiling point of liquid nitrogen is-195.8 ℃, based on liquid nitrogen explosion suppression, asphyxia, cooling and other features, aiming at the coal seam occurrence and production technology, through ground equipment, the use of mobile mine-used small tank of cryogenic liquid nitrogen to transport liquid nitrogen to underground fire prevention area, spontaneous combustion of coal mine fire hazards is effectively controlled with nitrogen injection by drilling, nitrogen injection pipe and other technology.Practice has proved that mobile nitrogen injection technology is preventable and curable for coal mine fire, and easy to underground production and post-fire recovery, especially as a large underground fire prevention treatment, it is an important technical mean in currently China's coal industry. It will play an important role in promoting China's coal mine safety production.