Abstract: Liquid nitrogen technology was based on the features that liquid nitrogen itself is small, easy storage and transportation, it gave full play to the multiple roles of liquid nitrogen, such as explosion suppression, asphyxia, cooling and so on. It utilized the methods that spilling liquid nitrogen directly to the fire prevention district and liquid nitrogen vaporized to be gas nitrogen which was injected to the fire prevention district, these methods can be widely used to deal with spontaneous combustion and external-origin fire in coal mines, they had the characteristics that preventable, extinguished, easy recovery after extinguishing. Practice had proved that the liquid nitrogen technology can be an important means to prevent and deal with large fire accidents under coal mines, it inevitably played an important role for the protection of safety production in coal mines of our country.