Under imitating human physiological solution, the fretting behaviors of flat cortical bone specimen from fresh human femur in the axial orientation against TA2 titanium ball with diameter of 40 mm had been investigated. The coefficients of friction (COF) and fretting logs were calculated automatically. The worn surfaces of the cortical bone were analyzed by means of laser confocal scanning microscopy. The results showed that the fretting logs for the cortical bone varied with the increase of the cycles from the elastic partial slip (D=5 (m), the elastoplastic partial slip (D=15 (m) to gross slip (D=30 (m), respectively. The fretting regime transformed from the partial slip regime directly to the gross slip regime without the mixed fretting regime. And the evolution of the COF in each fretting condition was also compared statistically. The fretting damage in the elastic partial slip state was slight. But the abrasive wear and micro-fracture were observed in the plastoelastic partial slip state and gross slip regime. The wear depth increased with cycles and well related to the COF of the cortical bone in each fretting condition. To reduce the fretting damages of bone, it is advisable to control the displacement amplitude at bone-implant interface.