The key friction pair of piston ring/cylinder liner in diesel engine due to its large cylinder diameter,long stroke and high-power output is prone to abnormal wear,resulting in the loss of diesel power performance,and even serious cylinder pulling accidents.Advanced surface treatment technology is an important approach to significantly improve the lubrication conditions and tribological properties of piston ring cylinder liner friction pair.DLC film with a thickness of 7 μm was prepared on the surface of Chrom-Keramik-Schicht（CKS）piston ring by cathodic arc ion plating technology,and the tribological properties of DLC film under simulated working conditions of diesel engine were studied.The results show that under the sever conditions of dry friction,lean oil at room temperature and lean oil at high temperature,the prepared DLC film can significantly reduce the friction coefficient of piston ring/cylinder liner friction pair and reduce the wear of CKS cylinder liner.The synergistic lubrication between DLC film and lubricating oil and the graphitization of DLC film during the operation are the main reasons to improve the tribological properties of friction pair between piston ring and cylinder liner.