Under high impact energy, nano-structured surface layers of Hadfield steel and annealed AISI 1045 steel were investigated in the present paper. It has been observed that a so-called "black layer" for Hadfield steel and "white layer" for AISI 1045 steel has been formed, respectively. That definitely will give rise to a change of wear mechanism. The wear tests showed that the wear weight loss curve of Hadfield steel will be bent down after some critical impact numbers. The wear curve of the AISI 1045 steel, however, shows a step-like characteristic with increasing impact numbers. It can be found from microstructural examination that high density twin bands of subsurface for Hadfield steel were produced, which have good plastic deformation coordination with bulk material. Cracks are usually initiated in the "black layer" underneath 12 gm in depth, and the worn debris sizes were also observed in nano-scale. Nano scaled wear controls the whole wear process. For the annealed AISI 1045 steel, cracks are mainly initiated between the interface of the "white layer" and sub-surface deformation layer. Debris is in micron-scale and spalled in the flake-like style. The wear weight loss is, therefore, greater than that of Hadfield steel. The result showed from the wear tests of Hadfield steel and AISI 1045 steel that nanocrystalized process of subsurface becomes one of control factors to affect wear losses and wear mechanism under high impact energy.