The absolute fineness of the ball diameter and the ball charge grading are important factors for the optimal operation of a ball mill. Therefore, the effects on breakage kinetics of the ball diameter and the fractional ball filling were investigated on the barite powder at batch grinding conditions based on a kinetic model. For this purpose, firstly, six different mono-size fractions were carried out between 0.850 and 0.106 mm formed by a 2 sieve series. Then, S-i and B-ij equations were determined from the size distributions at different grinding times, and the model parameters were compared for three different ball filling and three different ball diameter. The results of tests, the effect of ball filling and ball diameter on the grinding were found to be different than other investigators regarding some results. (C) 2011 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.