Abstract: Friction and wear tests were conducted on YH31 alloy cast iron piston ring and cylinder liner of different materials (high boron copper cast iron and CrMoAl cast iron)under lubrication conditions of lubricating oil without and adding 0.1wt% MoS₂.Influence of the lubrication condition and cylinder liner material on the friction coefficient, volumetric wear loss and wear surface morphology was studied, and the wear mechanism was analyzed.The results show that adding MoS₂ shortened the running in period of the piston ring and high boron copper cast iron cylinder liner, prolonged the stable wear period, decreased the friction coefficient and reduced the volumetric wear loss; the wear marks on the rubbing pair surfaces were finer and more shallow than those under the lubrication condition without MoS₂, and no cracks were found.Under the lubrication condition without MoS₂, the piston ring matched with CrMoAl cast iron cylinder liner entered the stable wear stage earlier than that matched high boron copper cast iron cylinder liner, but the stable wear stage lasted shortly, the average friction coefficient increased, and the volumetric wear loss increased greatly.The wear mechanism of the piston ring was polishing wear; the high boron copper cast iron and CrMoAl cast iron cylinder liner had abrasive wear+fatigue wear and abrasive wear mechanisms, respectively.