The comminution in Semi-Autogenous (SAG) mills depends on the impact conditions. It will be worthwhile to determine the efficient impact parameters. Drop weight test is employed to simulate the ball-flat impacts and study the effect of collision energy on ore breakage. Specimens are the copper ores of SAG mill feed of Sarcheshmeh copper complex. Minimum energy required for breakage is determined for each size. The size distribution of the broken ore due to the different specific input energies is determined and a relation is presented to predict it. Since the production of fine particles is important in SAG mill process, t 10 is measured and discussed. The results of present work can be used to optimize the comminution in SAG mills by controlling the milling parameters such as the mill speed, liner height and profile, feed size and ball size to achieve the efficient mill throughput.