The severe wear of separating ring is considered to be a main reason which leads to the improper declutch of the main clutch of heavy vehicles. The wear mechanism of the separating ring is not well understood. Scanning electron microscopy and transmission electron microscopy were employed to analyze the surface features and dislocation characteristics of the separating ring. The typical features of furrows and rolled tongue-like metal were found on the surface of separating ring by scanning electron microscopy observation, which can be considered as a major indi cation of the grain-abrasion. A zone of high density dislocation was noted on the subsurface of the separating ring by transmission electron microscopy observation, which implies the contribution of the severe impact on the surface of the separating ring in the wear process. The influences of the structure of the separating ring, the service condition and the in-service stress distribution on the wear behavior, were also analyzed. The results show that the failure of separating ring results from the impact wear and grain-abrasion together with the plastic deformation.