A plasma technique was applied to modify the surface of polytetrafluoroethylene (PTFE) fiber to improve the compatibility between PTFE and polyacetal (POM). This technique used argon (Ar) plasma to treat PTFE fiber first and then grafting the fiber with acrylic acid (AAc) by peroxidation. The Ar plasma-treated PTFE (PPTFE) fiber and AAc-grafted PPTFE (AAc-g-PPTFE) fiber were added into POM to increase the wear resistance and to decrease the friction coefficient of POM. The variables of the experiments were plasma treatment time, monomer concentration of AAc, and grafting time; The graft copolymer was characterized by Fourier transform infrared (FTIR) spectroscopy. The stress-strain behavior, impact strength, Taber wear factor, friction coefficient, and morphology of composites were also investigated. The properties of POM/PTFE composites could be successful modified by surface modification of PTFE in this investigation. The impact strength of POM/AAc-g-PPTFE composites was more than twice of that of POM/PTFE composites. The Taber wear factor and friction coefficient of POM/AAc-g-PPTFE composites decreased markedly.