Abstract: Optimum amount of rare earths(RE) for treating carbon fiber surface and effects of different surface treatments of carbon fiber on tribological behavior of Polytetrafluoroethylene(PTFE) composites under dry friction condition were investigated.Worn surfaces were observed and analyzed by scanning electron microscope(SEM).Experimental results showed that the best tribological behavior of the CF/PTFE composites was obtained when the content of rare earth elements was 0.3wt%.Under dry friction condition,PTFE composites filled with surface treated carbon fibers exhibited better tribological performance than those of the PTFE composite filled with untreated carbon fibers did.Rare earth elements acting as surface modifier of the carbon fibers can increase interfacial adhesion and toughness between carbon fibers and PTFE matrix,and it improved tribological performance of the composites.