Abstract: In the grinding process,we could obtain the desired particle size composition of the product by simply adjust grinding time and speed of mill,so realize the size distribution characteristics of coarse slime in the different grinding time and speed of mill. Conduct the rod milling experiments in the laboratory for study,on the basis of effect of grinding time and rod-mill speed on the rod-mill product size distribution of coarse slime,established the time-based grinding kinetics equation of-0. 25 mm and-0. 075 mm; then change the grinding time and speed of mill together to get the yield of the particle size of-0. 075 mm and 0. 075 ~0. 25 mm,according to principle of method of least squares to create the regression model of grinding time,speed of mill and the yield; according to the regression model we could get the yield of the particle size in any one grinding time and speed of mill,and we also could observe the trend of its forecast.