In this study, a new two-step plasma immersion ion implantation technique was developed and applied for the modification of Ti6Al4V alloy; firstly ion implanting with nitrogen at high temperature and followed with oxygen in high dose. A graded titanium oxide-titanium nitride film wasobtained on the surface of the Ti6Al4V alloy. The contact angle and the microhardness of the modified alloys were measured. The friction andwear properties of UHMWPE rubbing against the modified alloys under lubrication of distilled water were investigated using a pin-on-disctribometer. The wettability and the microhardness of the alloy surfaces were found to be increased significantly after ion implantation. The frictioncoefficient decreased by nearly 5 times and the wear resistance of UHMWPE increased by about 40 times against the ion implanted Ti6Al4V alloy.Many deep furrows were found on the surface of the un-implanted alloy and were absent in the ion implanted surfaces of the alloy.