The pairs of cylinder and piston ring of internal combustion engine made by gray cast and alloyed cast respectively by laser quenching were optimized. Wear experiments with enough lubricates showed that the best pair of laser hardening cylinder and piston ring is cylinder alloyed with phosphor. Chromium and molybdenum with piston ring alloyed with Chromium, molybdenum and copper which has much lower wear velocity than that without laser hardening.