Magnesium and nickel alloy was prepared electrochemically in dimethylsulfoxide (DMSO) solution. Its structure, composition and property for hydrogen storage were studied by SEM, ICP, XRD, and charge and discharge test. It is found that codeposition of magnesium and nickel can take place at the potentials from -2.0 to -3.2V (vs. Ag/Ag+) in 0.15 M LiClO4+DMSO solution containing MgCl2 and NiCl2. The surface morphology and the hydrogen storage capacity of the prepared alloy are influenced by the deposition potential. The alloy prepared at -2.4V (vs. Ag/Ag+) is mainly composed of Mg2Ni phase and shows its best electrochemical capacity of 361.8 mAh g(-1), corresponding to a hydrogen storage capacity of 1.35 wt.%. (C) 2009 Elsevier B.V. All rights reserved.