Abstract: Using JD-125 reciprocating impact wear tester, the surface of Bainite steel is separately impacted for 40 h to observe evolution of microstructure in surface and changes of wear rate. When the impacting energy is 6 J, the wear rate kept invariability all the time, which shows an usual wear rule ; When the impacting energy is 8.0 J, the wear rate sharply decreased after impacted 10 h and was lower than that of 6.0 J, an abnormal wear phenomenon occurred. With the help of HRTEM, a lot of amorphous phase was found in surface and some nanocrystalline embed in the amorphous basis. Because of the appearance of amorphous layer, usual wear mechanism was restrained strongly and its wear rate decreased, its surface topography is more even and smooth than that of 6.0 J. Result indicates that the amorphous layer can form only when the impact energy exceeds a certain threshold.