Base on the experimental result of the relation between rotating speed and balls movement in different type ball-grinding mill, the applied limitation of the classical rotating speed formula is pointed out. According to the real movement of balls in the mill barrel, its theoretical model is established, with which critical rotating speed and work rotating speed formulas are derived. The results calculated with the new formula is according with the experimental results and literature date. It isn’t difficult to determine the parameters, so that the new formulas can be directly used in production, which will bring great benefit. [
