Surface morphology of magnesium alloy irradiated by high-intensity pulsed ion beam (HIPIB) at energy density of 1.1-3.4 J/cm(2) with shot number from one to ten has been investigated by using scanning electron microscope and profilometer in order to explore the interaction mechanism between HIPIB and metallic materials. Three groups of samples with different initial surface roughness (R-a) were prepared to determine the effect of surface state on surface morphology. It was found that for the medium-roughness and high-roughness samples the irradiated surface represents a wavy feature and the formation of crater in local region due to selective ablation of the microprotrusions deriving from the rougher initial surface, however, no obvious craters were observed for the low-roughness sample, which exhibited texture feature and relatively mild irradiation damage. The mean spacing of surface profile irregularities (S-m) increases as shot number increases for various initial surface roughness samples. For low-roughness and medium-roughness samples R-a increases with increasing shot number, whereas R-a first increases slightly, and then decreases with increasing shot number for the high-roughness sample. It is also demonstrated that increasing energy density led to the increase in both R-a and S-m at all the shot number investigated, and the corresponding surface morphology altered from obvious craters at the lower energy density of 1.1 J/cm(2) to distinct droplet ejection feature owing to more intense energy deposition at the higher energy density of 2.3 and 3.4 J/cm(2). (C) 2012 Elsevier B.V. All rights reserved.