Abstract: To grasp the difference of different inert gas flame retardancy in different oxidation stages of coal, in this paper, an adiabatic oxidation device is used, and non-adsorbable helium is used as the reference gas to design inert （N₂、CO₂） flame retardant experiments with different initial temperatures （70、110、150℃）. Taking the temperature and oxygen concentration of the coal sample after inert gas injection as assessment indicators, the flame-retardant effects of different inert gases were compared and studied. The results show that the apparent activation energy of the experimental coal sample is 47 kJ/mol, and the critical temperature of spontaneous combustion is 83 ℃. The higher the initial temperature, the longer it takes to cool down to 30 ℃. After injecting different inert gases at the same initial temperature, helium has the best flame retardant effect, followed by nitrogen, and carbon dioxide is the worst. The replacement rate of nitrogen and carbon dioxide for oxygen increases with the increase of temperature. When the initial temperature is the same, the cooling rate and relative displacement of nitrogen injected are larger than those of carbon dioxide injected, and the flame retardant efficiency of nitrogen is better than that of carbon dioxide.