Abstract: In order to study the effect of particle size and air volume on the deposition, migration and distribution law of pulverized coal in the annulus of drill pipe and hole wall, the Euler-Euler model is used to numerically simulate the gas-solid two-phase flow formed by compressed air transporting pulverized coal particles against the background of air directional drilling into the hole in a broken soft coal seam. The higher the airflow, the smaller the particle size, the smaller the deposition of coal dust, the stronger the transport capacity of coal dust, and the corresponding pressure at the bottom of the pore is larger. Under the same airflow, the small particle size coal dust mainly appears to roll in a spiral line to transport to the orifice, while the large particle size coal dust is mainly located in the middle and lower part to move to the orifice along a specific trajectory.