To investigate the optimum diameter of milling balls in preparation of graphene by grinding method,the theoretical diameter of milling balls was calculated according to the principle of stirring ball mill and mechanism of graphene stripping. The optimum diameter of milling balls was verified through a designed experiment. The influence of milling ball diameter in graphene technology on grinding effect was analyzed. The results show that the optimum diameter of milling balls is 100 μm with current experiment...