Contacts model of Hertz-Mindlin (no slip) based on discrete element method of soft-sphere was used to simulate the impact action between the rice particles flow and the impact-board in order to improve the measurement accuracy of grain flow. The relationship of rice mass and mean normal impact force was analyzed when the line velocity of elevator was 0.5, 1.0 and 1.5 m/s. The results showed that simulation parameters of discrete element method which used between rice particles and impact-board were reasonable, and it had great practical value; The Linear correlation increased from 0.8062, 0.9082, 0.9891 to 0.9144, 0.9630, 0.9944 at three velocities respectively when the sliding stages removed. Therefore, we should consider how to reduce the sliding stages to improve the measurement accuracy when designed the measurement device of grain flow. This article can provide technical support for the research and development of grain mass flow device.