Abstract: To study the conduction mechanism of liquid nitrogen in coal,a porous media system based on glass wool was constructed.Then the heat transfer simulation experiment of liquid nitrogen in porous media system was carried out.The dynamic distribution of the temperature field in porous media was obtained by a thermocouple and a data collector to discuss the effect of liquid nitrogen injection quantity on the heat transfer characteristics of liquid nitrogen.The results showed that liquid nitrogen formed a cold concentration zone,which reduced the temperature locally.The cooling concentration zone mainly moved vertically downward.Meanwhile,the impact of injection quantity on the vertical moving speed was relatively small.This study provides a theoretical basis for the practice of liquid nitrogen coal fire extinguishing technology.