Abstract: In this paper the commercial software PHOENICS(v1.5) is used to simulate the turbulent flow in the grinding chamber of a pancake superfine jet mill. The predicted results of 3-D velocity fields and velocity vectographs are given. LDV measurements are made to validate the results predicted by PHOENICS. The predicted results show that the tangential velocities are the main components, the radial velocities are directed to the wall of chamber near the nozzles, the axial velocities are small but can not be neglected. The method of numerical simulation will improve the design of pancake superfine jet mill.