A new model, an enlarged particle model, is proposed for simulating behavior of numerous tiny beads in wet beads milling using discrete element method (DEM). The enlarged particle model is assumed to be composed of several tiny beads. The behavior of enlarged particles in the stirred mill was simulated numerically using DEM. Furthermore, an experiment measuring the bead velocity in a transparent milling chamber using a high-speed camera was conducted to validate the enlarged particle model. The behaviors of 2 and 3 mm beads in the stirred mill were also simulated using DEM. The velocity distributions of beads obtained from the simulation agree well with experimental ones when choosing the adequate frictional coefficient of beads. Then the virtual frictional coefficient was introduced into the enlarged particle model. The virtual frictional coefficient was determined so that the velocity distribution of the enlarged particles agrees with the distribution obtained from experiments. The adequate virtual frictional coefficient increases with an increase in the enlarged ratio, which is determined as a volume ratio of enlarged particle to bead. The correlation between the adequate virtual frictional coefficient and the enlarged ratio was apparent. (C) 2012 Elsevier B.V. All rights reserved.