Abstract: Based on the experiments of engine assembly and automotive road running, wear mechanism of engine oil pump chain was studied, the wear curves of automotive chains in different test condition were drawn respectively, the circular hardening and circular softening characteristics of the main parts of automotive chains were expounded. Wear surface morphology and impact fatigue flaw of the main parts of automotive chains were studied at micro scale. By measuring the force to pull out a component from a firmly assembled component combination, fretting wear of matching parts were analyzed. The main wear mechanism of automotive chains was fatigue, flaking of the surface of pin and bush. The roller was hardened circularly at high load and high speed with variation. The roller was softened circularly at common load and speed. The fretting wear between matching parts became severe with increasing of load and speed.