Based on the elastic hydrodynamic model of piston and connecting rod, the lubrication characteristics of piston pin and connecting rod small end bearing were studied. The finite element models of piston pin, connecting rod and piston were established, and the degree of freedom were reduced. Then the elastic hydrodynamic simulation model of connecting rod small end bearing was established. By analyzing the bearing lubrication parameters such as connecting rod small bearing oil film thickness, oil film pressure and rough contact pressure, the effects of various matching clearances and piston pin and connecting rod small end rigidity matching parameters on lubrication were studied and the cause of abnormal ablation for the bushing of connecting rod small end was analyzed. The results show that the rigidity matching between piston pin and connecting rod small end and the clearance of connecting rod small end have great influence on the bearing lubrication characteristics.