Abstract: The morphology, elemental distribution, and chemical states of some typical elements on the original and worn surface of Au rare earth alloy wire sliding against Cu 40 NiZnMnCe alloy ring were investigated by means of scanning electron microscopy, electron probe microanalysis, and X ray photoelectron spectrometry. Then the wear mechanisms of the Au rare earth alloy wire were discussed based on the related surface analytical results. It was showed that the alloy wire was characterized by slight adhesion wear and oxidation at extended test duration. The rare earth elements in the alloy wire diffused onto the surface and segregated at Au rich zones owing to the temperature rising during the sliding process. The elements Cu and Ni were oxidized in the sliding process, with the formation of Cu 2O and Ni 2O 3, while friction did not lead to change of chemical state of Au. The oxidized products helped to keep off the frictional pair contact, and hence to decrease the surface energy of the alloy wire. This partly accounted for the decrease in the friction coefficient and wear rate of the Au rare earth alloy wire sliding against Cu 40 NiZnMnCe alloy ring.