Abstract: The paper derived two regressive equations between the characteristics and all the main parameters of high grade hammer miUls based on the collccion of the experimental data of hammer mills all over the China. According to the regressive equations the author made a diagram to show the relationship between all the parameters. The author also found out the pattern of the influence of each parameter on the indexes of the characteristics of a hammer mill by analysing the relationship between them with the regressive equations and the diagram. Due to the high precisiocn of these two regressive equations, anyone can use them to predetermine the operation indexes of a hammer mill. In other words, by the known values of all the parameters the user can use these regressive equations to predetermine the indexes of the mill to be selected. Meanwhile, engineers can design a hammer mill with their required indexes by these regressive equations.