Abstract: In inert gas fire prevention and extinguishing technologies, N₂ and CO₂ are widely used in the field of coal mine fire prevention and extinguishing. This paper based on the local fire control measures in tail roadway of a mine in Inner Mongolia with N₂ injection first and liquid CO₂ injection later, analyzed the change of gas concentration in the fire area after adopting the combined inert gas fire prevention and extinguishing technology, and compared the fire prevention and extinguishing performance of N₂ and liquid CO₂ to the local fire in tail roadway. The conclusions are as follows: large amounts of N₂ injection into the combustion zone can effectively dilute the concentration of O₂, but the hidden danger of re-burning has not been eliminated in this coal fire prevention and control; low temperature CO₂ from liquid to gaseous reduces the oxygen concentration rapidly to 3% by diluting the oxygen concentration and reducing the external air leakage more effectively; compared with N₂, CO₂ has better diffusivity and dilution effect. The dilution effect of CO₂, C₂H₄ and C₂H₆ is more obvious, which shows that CO₂ can better reduce coal oxidation reactivity. Practice has proved that liquid CO₂ is superior to N₂ in preventing local coal fires.