Abstract: In order to effectively prevent and control the coal mine spontaneous combustion fire hazard, the research on the technology of cryogenic inert gas slurry was carried out aiming at the shortcomings of the existing inert gas fire-fighting technology, such as poor cooling effect and complicated conveying process. The experimental system for the preparation of cryogenic inert gas slurry and the cooling of heated loose coal was independently designed, and the temperature changes at different measuring points and the concentrations of CO and O₂ in the experimental chamber were obtained under different injection flow rates. Results show that LCO₂ （ｌｉｑｕｉｄ ＣＯ₂） is mixed with LN₂（ｌｉｑｕｉｄ ｎｉｔｒｏｇｅｎ） in the pipeline transmission process, and injected into the experimental chamber in the form of solid, liquid and gas three-phase. The phase change occurs rapidly, the ordered structure is damaged, and a large amount of heat is absorbed. The temperature of air and coal in the box drops rapidly, and the fire prevention performance is better when large flow rate is injected. By comparing the fire-extinguishing effect of injecting liquid nitrogen and liquid carbon dioxide separately, it is concluded that the anti-fire-extinguishing technology of inert gas slurry has the advantages of both liquid nitrogen and liquid carbon dioxide, and the cooling and oxygen reduction effect is significant, and the anti-fire-extinguishing effect is better than that of liquid nitrogen and liquid carbon dioxide.