In this study, the effects of graphene as an additive on the tribological properties of ultra-high molecular weight polyethylene (UHMWPE) were studied by molecular dynamics simulation. The results showed that the frictional force decreased with the increase of graphene content in the friction model that graphene was located at the friction interface between iron and UHMWPE. Meanwhile, the plastic deformation of UHMWPE was also weakened. When the graphene is located in the subsurface layer of UHMWPE, because of the attractive interaction between the graphene and surrounding polyethylene chains, the plastic deformation of surface UHMWPE decreases with the increase of graphene content. At the same time, it was found that the graphene had a tendency to diffuse into UHMWPE during the frictional process. As a result, the polyethylene chains around graphene disentangled more slowly, which weakens the plastic `deformation of the surface UHMWPE but causes the increase of the frictional force of UHMWPE. Keywords: UHMWPE, Graphene, Friction, Deformation, Molecular Simulation