Abstract: The tribological performance of diamond film and graphite/diamond composite film under paraffin oil lubrication was compared on an SRV friction and wear test rig. The surface morphologies of the films and wear tracks were observed with a scanning electron microscope. The wear volume losses of the film specimens were determined with a profilometer. The wear mechanisms of the films are discussed as well. The results show that with paraffin oil lubrication the friction coefficient and wear volume loss of graphite/diamond composite film are lower than those of the diamond film. Both the diamond film and graphite/diamond composite films are characterized by sub-micro-fracture and adhesion wear in sliding against the ceramic counterpart under the lubrication of liquid paraffin.