Abstract: In order to study the influence of inert gas on coalbed gas and coal dust mixed combustion flame, a Hartmann tube with a vertical opening of 68 mm and a height of 300 mm was used in the experiment. Taking coalbed gas and coal dust mixed combustion flame as the research object, the influence of CO₂ and N₂ was studied. The results show that when CO₂ concentration was 0, 5%, 10% and 15%, the maximum propagation velocity of the flame was 7.1 m/s, 4.6 m/s, 3.8 m/s and 2.6 m/s, respectively. With the increase of CO₂ concentration, the rate of coalbed gas and coal dust combustion decreased continuously. When N₂ concentration was 0, 5%, 10% and 15%, the maximum flame propagation velocity was 7.1 m/s, 6.9 m/s, 4.2 m/s and 3.9 m/s, respectively. With the increase of N₂ concentration, the rate of coalbed gas and coal dust combustion decreased continuously. By comparing the effects of two inert gases on the mixed combustion of coalbed methane and coal dust, the effect of carbon dioxide on the flame propagation velocity of the mixed combustion was significant.