<p>The ball and powder filling rate are common operation parameters for the operation of stirred mills. However, their impacts on the evolution behavior of particles of stirred mills are not fully understood yet. In this study, the effect of the breakage rate, the breakage distribution function, the grinding time at special points and the specific energy input adjusted by varying the ball and powder filling rate was investigated. The evolution behavior of the particles during the grinding process was examined with the population balance model (PBM). The volume fraction of each size interval was back-calculated with the simulated parameters of PBM. The volume fraction of each size interval in the grinding products at both the peak point and the switch point was discussed. Furthermore, the relationship between the contour plot of the volume fraction of the target size with the ball and powder filling rate was examined by the grinding time and the specific energy input. The result reveals that the energy efficiency of stirred mills is higher at a relatively high ball filling rate and a relatively lower powder filling rate. It has been demonstrated that a ball filling rate of 56% and a powder filling rate of 0.70 represent the optimal condition. Under this condition, the highest proportion of the target size fraction can be attained with the lowest energy consumption and a relatively high time-effectiveness.</p>