The chemical composition and microstructure of the metal alloys are one of the most important factors in the metal-hydrogen system. In this work, hydrogen storage nano-scale 2Mg-Ni/Ni, Mg₂Ni/A, LaNi₅/A, ZrV₂/A (A=Ni, Pd) and Mg₂Ni/LaNi₅, Mg₂Ni/ZrV₂ composites have   been synthesized using the mechanical alloying process. Structure, hydrogen storage capacities and the electrochemical discharge capacities of the new materials have been measured. Results showed that the XPS valence bands measured for MA nanocrystalline alloys and composites showed a significant broadening compared to those obtained for microcrystalline materials. Additionally, the nanocomposite structure reduced hydriding temperature and enhanced hydrogen storage capacity of Mg-based materials. For example, the results show that nanostructured Mg_1.5Mn_0.5Ni/LaNi_3.75Mn_0.75Al_0.25Co_0.25 composite material release 1.6 wt% hydrogen at room temperature. The observed effect of LaNi_3.75Mn_0.75 Al_0.25Co_0.25 nanopowder on hydrogen storage behaviour of Mg_1.5Mn_0.5Ni phase strongly suggest that all the improvement of hydrogen storage properties is due to kinetic effect of LaNi₅ nanopowder acting as a powerful catalytic rather than to a modification of thermodynamic properties of the Mg_1.5Mn_0.5Ni + LaNi_3.75Mn_0.75Al_0.25Co_0.25 system. Additionally, doping Mg_1.5Mn_0.5Ni nano-composite material with ZrV₂-phase reduces the dehydriding temperatures, as well. Surface segregation effect and valence band broadening observed in the measured nanocomposites could significantly influence their hydrogenation properties. The nanocrystalline Mg-based hydrides offer a breakthrough in prospects for practical applications.