Wear is the primary cause of failure of joint replacement prostheses. In this paper, the ultrahigh molecular weight polyethylene(UHMWPE) was implanted with Oq and Cq ions at different energies and doses. Its friction and wear behaviors were studiedunder dry friction, lubrication of distilled water and blood plasma using a pin-on-disk tribometer with a Si3N4 ceramic ball as thecounterface. Scanning electron microscopy was used to examine the surfaces of un-implanted and implanted UHMWPE beforeand after wear. The experimental results show that the wear resistance of the implanted UHMWPE is higher than that of the unimplantedUHMWPE under dry friction, lubrication of distilled water and blood plasma. The wear resistance of the Oq-implantedUHMWPE is better than that of the Cq-implanted, especially for 450 keV energy and 5=1015ycm2 dose Oq-implanted sample,of which the wear rate is the lowest. The wear rates of the implanted and un-implanted UHMWPE are higher under dry frictionthan under the blood plasma lubrication. The adhesion, ploughing and plastic deformation are the wearing mechanisms for theun-implanted UHMWPE, while the fatigue and abrasive wear for the implanted UHMWPE.