Abstract: Based on lots of video observation tests, there are three motion states of grinding medium in a mill tube, including projection, revolution and autorotation. The movement cycle of grinding medium departing from and contacting with the inner liner is equal to the vibrating period. By building an impulse transfer model, the distribution laws of impulse transfer, energy transfer and energy dissipation are discussed, and the mechanism of the vibrating mill is revealed. Finally, this paper proposes the ways to reduce the inertia region in the grinding tube and to improve the efficiency of grinding.