Abstract: The fretting fatigue behavior of TC4 alloy was investigated using cylinder-plane configuration.Based on the experimental results,the damage mechanism of fretting fatigue failure was discussed.The damage of fretting scar edge was caused by adhesive wear,and the center part of fretting scar was damaged by abrasive wear and contact fatigue.Fretting fatigue crack initiation tended to occur in fretting scar,especially from grinding pits.There were two factors responsible for specimens damage,one was the plastic deformation of the material layers adjacent to the contact surface caused by normal stress and tangential friction,another was the effect of notch stress concentration caused by surface damage.