The artificial joint simulator is designed to simulate the complicated movement and environment of the artificial joint in vivo. Although the wear loss of materials evaluated on the artificial joint simulator under ISO standard is found to conform to that in vivo, there is a significant difference in the morphology of the wear debris obtained from the tester and human body. It is well known that the wear debris plays an important role in aseptic loosening of the artificial joint, and its morphology indicates the working conditions of the artificial joint. Therefore, it is necessary to distinguish the two kinds of wear debris. In this paper, the comparative study of ultra high molecular weight polyethylene (UHMWPE) wear debris from the implanted artificial joint and hip joint tester was performed on their size distribution, shape, 3-D feature, and thickness. Results show that the wear debris from joint simulator have different sizes and shapes such as strip, block, plate, and spherical etc., their average diameter is 7.54 mu m, and its medium diameter is 6.89 mu m. The most wear debris from artificial joint have the spherical or subsphaeroidal shapes, and a small amount of the debris have the unbroken plate structure, the average diameter is 1.33 mu m, is about 18% of the wear debris' from joint simulator, and the medium diameter of 2.95 mu m, is about 43% of the wear debris' from joint simulator. The results are expected to provide both experimental and theoretical foundation for improving the artificial joint simulator and optimizing the evaluation standards of the artificial joint materials. (C) 2011 Elsevier B.V. All rights reserved.