Display omitted •DEM-CFD one-way coupling simulation represents the airflow and particle behavior.•Fluid flow in the spiral jet mill is not a simple spiral flow pattern.•Particles are mal-distributed near the inner wall of the grinding chamber.•Particles near the top and bottom walls collide at high speeds.•Spiral jet mill could grind the particles circulating near the top and bottom walls. Collision behaviors of particles in spiral jet milling were analyzed by using a simulation. The motion of the particles was tracked by the discrete element method (DEM), and the air flow was represented by the computational fluid dynamics (CFD). The DEM was coupled with the CFD by a one-way coupling method. The simulated air flow was validated by comparing the fluid velocity field with the measured one in a model experiment. Furthermore, the air flow and particle behaviors in a spiral jet mill used commercially were analyzed by using the simulation. As a result, the particles with a region balancing between centrifugal and radial drag forces could be mainly ground by the high-speed collisions between the particles circulating near the top and bottom walls of the grinding chamber.