The artificial joint acetabular material ultrahigh molecular weight polyethylene (UHMWPE) was reinforced with carbon fibers (CF) indifferent contents. The effects of CF content on hardness and tribological properties of the materials were studied. The morphologies of wearsurfaces were examined with a Scanning Electron Microscope (SEM). The results show that the hardness and wear resistance of CFreinforcedUHMWPE composites increased with CF content; the friction coefficients under distilled water lubrication were decreased greatlyby the addition of CF; that adherence, plowing, plastic deformation and fatigue wear are dominant for the UHMWPE under dry sliding, andthat abrasive wear and drawing out of CF from the wear surface of the composites are dominant for the CF-UHMWPE composites under bothdry and distilled water lubrication conditions.