Abstract: In order to solve the problem that the liners of Φ5.5 m×1.8 m SAG mill were easy to wear and fracture in a concentrator in Xinjiang. Firstly, the optimum structural parameters of cylinder liners were determined by the orthogonal test. Secondly, The discrete element method (DEM) was used to simulate the real operation of SAG mills. Based on the different structural parameters of cylinder liners (height, width and angle of lifter bars), the motion of particles and the change of collision energy in SAG mills were studied. Finally, the feasibility of the optimization scheme was verified by industrial tests. The results showed that a suitable parameters of the liners can effectively optimize the motion of particles in the mill, increase the effective collision of ball to ore and ore to ore, reduce the wear of liners or grinding media caused by invalid collision, and thus improve the operating parameters of the semi-autogenous mill. The optimum parameters of the lifter bars were determined by orthogonal experiment to be 190 mm in height, 140 mm in width and 60 ° in angle. The optimum parameters of liners were used to carry out industrial tests. The results showed that the optimized liner service life, mill operation rate and efficiency were increased by 51 days, 16.36% and 15.55 t/h, and the mill power consumption decreased by 6.07 kW·h/t. The results verified the reliability and superiority of the discrete element method and the orthogonal design method in the modification of the cylinder liners.