In order to study the flow field characteristics and pressure distribution in the grinding chamber during the working process of the grain milling machine of the grain mill, explore the influence of different working parameters of the milling mechanism on the milling effect, and study the use of Fluent to move the milling mechanism. The numerical simulation of the grinding flow field under different working parameters such as 750 r/min, 1000 r/min, 1500 r/min and feeding speeds of 0.5 kg/min, 0.75 kg/min and 1 kg/min were carried out. The results show that the dynamic pressure contour in the flow field is distributed in a ring shape, and its value increases as the radius of the grinding disc increases and the disc gap decreases. When the shape of the grinding disc changes, the dynamic pressure value will increase sharply, that is, the pressure of the powder particles increases, and it is more likely to be broken. Therefore, the shape of the grinding disc can be changed to increase the dynamic pressure and improve the grinding effect. When the disc clearance is 0.05 mm, the optimum grinding effect is obtained when the rotating disc speed is 1500 r/min, and the maximum grinding speed is between 0.5 kg/min and 0.75 kg/min.