Abstract: To clarify the wear characteristics of the discharge grate in a semi−autogenous (SAG) mill and predict its service life, a numerical simulation method for grate wear was proposed based on an improved Discrete Element Method (DEM) and the Shear Impact Energy Model (SIEM). The wear rate, service life, and tangential collision energy proportion of the grate under different ore filling levels and lifter shape parameters were analyzed. The results indicate that introducing the coefficient of restitution correction into the DEM effectively improved the numerical simulation accuracy, reducing the mean absolute error of the wear simulation for the lifters and the end liners by 13.47 mm and 22.26 mm, respectively. It was also determined that the wear of the outer circle lifters is the primary cause of grate failure. Furthermore, through quantitative evaluation of the grate wear rate under different conditions, it was found that increasing the ore filling level to 30% can extend the service life by 143 h and increase the proportion of effective collision energy at the discharge end by 2.53%; reducing the lifter bend angle to 25° and raising the lifter height to 160 mm can extend the service life by 1114 h and 3462 h, respectively, but will reduce the proportion of effective collision energy by 0.45% and 1.78%, respectively. This study provides theoretical support for the production maintenance and structural optimization design of SAG mill discharge grates.