Polymer composites reinforced by pristine and functionalized graphene are investigated to identify the improvement of tribological properties of polymer composites. A pull-out process is conducted to study the interfacial interactions between polymer matrices and graphene reinforcements using molecular dynamics simulations. Molecular layer models containing Fe atoms as the top nano-layer are built to study the enhancement of tribological properties of the polymer composites by sliding the top Fe nano-layer on the surface of the polymer matrix. The simulation results show that decreases of about 13% and 42.3% in the average friction coefficient and abrasion rate of the functionalized graphene/polymer composites can be achieved. In order to provide the understandings of the findings, the interfacial interaction energy, RDF values between graphene and polymer matrix are particularly calculated and discussed.