Abstract: In order to optimize the two-stage grinding process index of Meishan Iron Mine，aiming at the problems of low yield and substandard fineness of easy selecting grade in the grinding products of the two-stage ball mill，the experimental study on the influence of steel ball gradation，medium filling rate and grinding concentration on the grinding effect is carried out.The experimental results show that when the ratio of ϕ60 mm and ϕ40 mm replenish steel balls is 40%:60%，the filling rate is 42%，and the grinding concen‐ tration is 75%，excellent grinding effect can be obtained.Compared with the original scheme on site，the yield and grinding fineness of the easy selecting grade are increased by 16.92 and 10.66 percentage points respectively.Reasonable optimization of steel ball grading，filling rate and grinding concentration can effec‐ tively improve the quality of grinding products，and has important guiding significance for optimizing the grinding process index of the concentrator.

Key words: two-stage grinding, steel ball grading, filling rate, grinding concentration