In this study, the effects of powder filling were investigated on natural amorphous silica at batch grinding conditions based on a kinetic model. For this purpose, first eight different mono-sized fractions were carried out between 1.7 and 0.106 mm formed by a root 2 sieve series. Then, S-i and B-i,B-j equations were determined from the size distributions at different grinding times, and the model parameters (S-i, a(T), alpha, gamma, phi(j) and beta) were compared for four different powder fillings (5, 10, 15 and 20%). Finally, model parameters for every test and interstitial filling fraction (U = f(c)/0.4 J), taking into consideration the effects of the powder filling (f(c)), were discussed with respect to maximum mill capacity. In this study, it was found that the optimum value of U for the highest mill capacity is above 166.7% for an effective ratio for natural amorphous silica. Regarding the effects of powder filling on the grinding process, this study found results different from other investigators.