Abstract: It was showed by running on the road that wear characteristic of bushes and bearing pins of roller chains for the motor cycle is abrasive wear,together with stress fatigue wear;it was demonstrated by microstructure analysis and lengthened amount of the worn chains that both morphology of wear surface and wear resistance could be improved by high initial surface hardness.In the case of abrasive wear was the main mechanisms for the two matels,low surface hardness of the bushes and bearing pins of roller chains tend to produce large ploughing grooves,obvious characteristics of cyclic hardening and severe wear.Under oil pool lubrication,rate of crack propagation is large and cyclic softening is obvious when surface hardness of the bush and bearing pin is high.Cyclic hardnening occoured when surface hardness of the bush and bearing pin is low.It is concluded that both cyclic softening and hardnening is one of the reasons for the severe wear.