An influence of the operating parameters on the grinding performance of the wet bead mill has been researched experimentally and by using a simulation technique based on the discrete element method (DEM). The rotational speed of the agitator, the beads filling ratio, their diameter and material, and the slurry concentration were the subjects of the investigations. The grinding rate constant of the gibbsite sample was determined experimentally and compared with the specific impact energy calculated from the velocity of the grinding beads simulated. An increase in the rotational speed of the agitator and in the filling ratio and a decrease in the slurry concentration cause an increase in the grinding rate constant. A similar effect of the operating parameters on the specific impact energy has been observed.