Abstract: The process of ignition and flame propagation of pulverized coal particles under O₂/CO₂ atmosphere in a long quartz tube was recorded by a high-speed video camera. The coal ignition and flame propagation characteristics of the coal particles with different ratios of the diameter of 16 μm and 82 μm at different concentration of O₂/CO₂ atmosphere and air were analyzed. The results show that the pulverized coal size distribution plays a significant effect on the coal particles ignition and flame propagation; the coal particles with small size display a shorter ignition process and longer flame propagation distance; mixing the small size coal particles to the large size coal particles can shorten the ignition time, and increase the flame propagation speed; increasing the oxygen content can improve the flame combustion range and the more the small size coal particle ratio is, the more obvious the influence of oxygen concentration on combustion flame propagation speed is.