Abstract: Experiments on the plain bending fatigue and bending fretting fatigue for cyclic softening material tempered 42CrMo steel are carried out in this study. The difference between the plain bending fatigue and bending fretting fatigue mechanisms is identified, and the influence of cyclic bending load on the fatigue lives is discussed. The morphology of fracture surface under different bending loads and the fretting damage characteristics under different numbers of loading cycles in the bending fretting process are also investigated, with a view to studying the damaging mechanisms of bending fretting fatigue. Results show the lifespan of tempered 42CrMo steel under the bending fretting fatigue is much shorter than that under the plain bending fatigue, subjected to the same bending load. The fatigue lifespan of tempered 42CrMo steel decreases as the cyclic bending load increases under bending fretting fatigue. The local contact fatigue and the local plastic deformation due to bending fretting cause initiation and further propagation of fatigue cracks.