Abstract: Fretting damage on shaft surface in torsion was studied by using JD-1 wheel/rail simulation tester, and the effect of vertical load on fretting damage characteristic of interface fit between shaft and inner surface of bearings was investigated. The fretting damage mechanism of shaft surface was analyzed by observing the surface wear scar and microstructure of cross section of specimens by using laser scanning confocal microscopy and scanning electronic microscopy. The results indicate that the fretting damage appeares on the interface fit between shaft and inner surface of bearings at vertical loads, the wear is mainly in the form of adhesive wear and abrasive wear. Under higher vertical load condition, the wear on the surfaces of shaft is more serious, plastic layers in the interface fit both become thicker, the fretting damage becomes severer, moreover, the wear and plastic deformation on the left surface are severer than those on the right surface, and the thickness of the plastic layer is uneven.