Abstract: A coupling agent, rare earths, and a mixture of coupling agent with rare earths, were used to modify the surface of glass fiber, in an attempt to improve the interfacial adhesion between the glass fiber and polytetrafluroethylene (PTFE) matrix. The friction and wear behavior and the limiting pv values of the PTFE composites filled with the surface modified or unmodified glass fibers in oil lubricated sliding against steel were investigated with an MPV 20 friction and wear test rig. The wear mechanisms of the composites were analyzed based on morphological observation of the worn surfaces with a scanning electron microscope. The results show that the PTFE composites filled with surface modified glass fiber record lower friction coefficients and better wear resistance than those filled with the unmodified glass fiber, under the oil lubricated condition. The PTFE composite filled with rare earth modified glass fiber exhibits the lowest friction coefficient and the highest wear resistance as well as limiting pv values. This is attributed to the improvement of the interfacial adhesion between the surface modified glass fiber and the PTFE matrix. The composite filled with unmodified glass fiber is characterized by adhesion and transfer in sliding against the steel, those filled with the coupling agent modified glass fiber and with coupling agent and rare earth modified glass fiber are characterized by abrasive wear, while the PTFE composite filled with rare earth modified glass fiber by adhesion wear and slight abrasive wear.