［［Objective ］］ Designed a roller mill and optimize the structure of the milling system.［［Methods ］］ Using the Rocky DEM discrete element method,determined the structural range of key parameters such as the speed ratio of the milling system,roller diameter,tooth top width,and fast roller speed based on the particle size quantity of 1~5 mm.Orthogonal experiments were designed,and the particle numbers in each interval of 1~2,2~3,3~4,and 4~5 mm were obtained by simulation models.The four interval indicators were assigned to the weight using hierarchical analysis.Further the four indicators were integrated into a comprehensive value as the basis for judging the experimental results through TOPSIS.The grinding performance was measured in terms of the comprehensive value and the optimal structure was analyzed visually.［［Results］］ Compared with the initial structure,the number of grinding refined particles increased by 10 196,and the performance of scratch system improved by 14.2%.［［Conclusion ］］ The diameter of the grinding roller has the most significant impact on the grinding effect.The optimal structure for the rollermill includes a grinding roller diameter of 270 mm,a fast roller speed of 700 r/min,a speed ratio of 2.7,and a tooth top width of 1.2 mm.