The objective of this study was to investigate the effects of various sliding wear test conditions on the tribological properties of UHMWPE. The results indicated that the wear resistance of UHMWPE in the sliding direction perpendicular to the melt flow direction was stronger than that in the sliding direction parallel with the melt flow direction. It was found that the X-Z plane obtains more serious incomplete molecular bondings and cracks than the Y-Z plane. The main wear mechanisms were plastic deformations and wrinkled formations. The UHMWPE hardness increases or decreases as the applied load and sliding frequency increases or decreases.