The effect of pulsed high-energy electron beam on the surface modification of AZ91 magnesium alloy has been studied. The results show that the re-melted coatings (20~60 mm in thickness) on the surface of AZ91 magnesium alloy has been obtained under different treatment conditions. It was found that the thickness of the melted surface layer varies with the electron beam current and numbers of pulses, but the voltage has a minimal effect. The intensity of the diffraction peak assigned to Mg17Al12 increases with the increase of the electron beam energy, and a metastable AlMg phase has also been found from the XRD patterns of the treated AZ91 alloy. The treated surface layer exhibits a higher hardness than the AZ91 alloy, and the hardness of the topmost layer is two times as higher as the substrate. The friction coefficient and the wear volume of AZ91 alloy after electron beam treatment decrease obviously. The wear resistance of treated samples increases obviously, may be due to the high hardness from the grain refinement