Abstract: To evaluate the impact of cylinder liner modification on the operational efficiency of a large semi-autogenous mill,a comparative industrial study was conducted on metal cylinder liners and rub ⁃ ber-steel composite cylinder liners in the concentrator of a large open-pit porphyry copper mine ,address⁃ ing the optimization of efficiency and steel consumption during liner selection and use.Under the same op⁃ erating conditions,the operational performance indicators of the two liner types were statistically analyzed. The results show that the rubber-steel composite cylinder liner exhibited issues such as easy detachment of wear blocks and significant deformation in the later stage of use.Its ore throughput was at least 5.41%low⁃ er than that of the metal cylinder liner,and the specific steel ball consumption increased from 0.517 kg/t to 0.566 kg/t,representing a 9.48%increase in steel consumption.It is concluded that under the given ore properties and operating conditions,the application performance of the rubber-steel composite cylinder lin ⁃ er is inferior to that of the metal cylinder liner.The findings provide a practical basis for the modification , selection,and engineering application of large semi-autogenous mill cylinder liners.