Abstract: Fracture morphology, chemical composition, hardness and microstructure were analyzed to find the fracture reason of traction motor rotation shaft and pinion shaft of a locomotive which were interference fit. The results showed that the rotation shaft and pinion shaft were all rotation bending fretting fatigue fracture, the main reasons of fracture were the fretting abrasion of the interference surface between rotation shaft and pinion shaft and stress concentration on the junction of the pinion shaft′s oil groove and hole, fatigue cracks initiated because of the stress concentration, and then extended under the action of rotation bending stress to fracture finally. The crack initiation and fracture of pinion shaft were earlier than those of rotation shaft.