Abstract: Main wear on roller chain of walking machinery in agriculture is abrasive wear. Ploughing phenomenon showed that increases of hardness of bush and pin can improve its surface shape by wearing and improve its wear proof performance. When bush and pin of roller chain are lubricated by oil, propagation of fatigue crack is main factor to effect on lifetime of these parts. And the higher the hardness,the faster propagation of fatigue crack is, the larger separation hole caused by shape of wear surface is.