Abstract: As potential good candidates for high-capacity MH-Ni batteries and excellent applications,the hydriding and dehydrogenating properties of magnesium-based hydrogen storage alloys have been extensively studied.The influence of nanocrystalline particles and catalysts on the hydriding and dehydrogenating properties of magnesium-based hydrogen storage materials are summarized in this paper.The hydriding and dehydrogenating properties of magnesium-based hydrogen storage composites and some new basic theory results getting from a first-principle plane-wave pseudopotential method based on density functional theory(DFT) are introduced.It is pointed out that the theory calculation method is more and more important with the development of quantum chemistry and condensed matter as well as the improvement of computational ability and computational speed.