Aseptic loosening is one of the main failure modes in artificial joints. Significant information about the aseptic loosening is carried by the wear debris of the joints. In this paper, the wear debris acquired from the ultrahigh molecular weight polyethylene (UHMWPE) artificial joints is prepared and a systematic research is carried out to investigate the wear mechanism of aseptic loosening using the wear debris analysis. The hip joint simulator was used to conduct the wear tests of the CoCrMo-UHMWPE artificial joint friction pairs. The scanning electron microscope (SEM) was employed to analyze the wear debris profiles. The analysis results demonstrated that the UHMWPE joints mainly produced the roundness, tuberous, lacerated, sheet, pole-liked and strip wear debris, and the wear mechanism of the joint aseptic loosening had a close relationship with the morphology of the debris types. The adhesive wear, fatigue wear and laceration under alternating stress were the main causes of the joint failure. Based on the wear debris analysis results, a new diagnosis method using the radar map fractal representation was proposed to diagnose the failure of the artificial joints.