The increase of temperature will lead to the material degradation so that the deformation of connecting rod small end and the poor contact state between the connecting rod and the bushing occur, which may cause the poor lubrication of connecting rod small end and the loosening of bushing. The influence of material degradation on the deformation of connecting rod small end bore at high temperature was analyzed by using multibody system dynamics and finite element simulation. The results showed that the deformation of connecting rod small end bore was too large to keep good lubrication with the piston pin beyond 150 ℃. Additionally, the influence of material degradation on the contact state of connecting rod and bushing was analyzed by the finite element simulation. It was found that the increase of temperature would lead to the enlargement of slip zone and the reduction of adhesion zone so as to make the bushing to loosen more easily. Besides, the influence of material degradation on the binding force between connecting rod and bushing was analyzed through the extrusion experiment of bushing. The binding force decreased sharply when the temperature dropped to room temperature from 300 ℃. The finite element simulation also proved that the large plastic deformation had occurred at 300 ℃, which could not recover at room temperature and hence cause the slip and even loosening of bushing easily.