Abstract: Aiming at the problem of self-heating and spontaneous combustion problem for coal mine open-pit coal piles, in order to study the influence of coal particle size on the spontaneous combustion of coal,the theory of porous media, heat transfer, fluid mechanics and other theories was usedto establish a coal pile’s self-ignition based on a coal pile as a prototype, a two-dimensional model of self-heating and spontaneous combustion of the coal pile was established. Using COMSOL software to simulate and analyze the internal temperature, oxidation oxygen consumption rate and air leakage rate law of coal piles with different particle sizes (0.5～35.0 mm) under different wind speeds (0.05～13.00 m/s), according to the simulation results, the change curve of the maximum temperature of coal piles of different particle sizes under different wind speeds was obtained.Then the range of spontaneous combustion wind speed of coal pile with different particle size were divided, and the minimum, maximum, and maximum temperature of coal piles of different particle sizes were obtained. The results show that in addition to the particle size of 0.5 mm and 2.0 mm of coal, the maximum temperature inside the coal piles with other particle sizes shows a “rapid increase-maximum value-rapid decline-stable at a relatively low value” as the wind speed increases.The difference is that with the particle size of the coal pile, the rate of temperature rise and temperature drop is different, and the stable temperature that can be reached under higher wind speed conditions is also different.When the natural wind speed is less than 1 m/s, the smaller the average particle size of the coal pile is under the same wind speed, the lower the maximum temperature inside the coal pile.When the natural wind speed is greater than 1 m/s,the average particle size is smaller than under the same wind speed. The 10 mm coal pile has a higher temperature. When the average particle size is 0.5 mm, spontaneous combustion generally does not occur; when a pile of coal particle size≥1 mm, there were different degree of spontaneous combustion in different wind speed ranges. When the average particle size of the coal pile≤10 mm and when the spontaneous combustionJP3 wind speed≤1 m/s, the smaller the particle size, the lower the maximum temperature of the coal pile;when the natural wind speed＞1 m/s, the smaller the particle size,JP the higher the temperature of the coal pile.