Mg–Ni composite hydrogen storage materials have been prepared by high energy ball milling Mg and Ni powders and annealing in hydrogen atmosphere forming Mg2Ni catalytic phase. Mg65Ni35 (wt%) alloy can desorb 3.4 wt% H2 at 290°C and 4.8 wt% H2 at 305°C in 40 min. The improved desorption properties are attributed to the homogeneous distribution of nanocrystalline Mg and Mg2Ni phases. The structure and storage properties are not changed through 150 cycles of absorbtion at 300°C and desorption at 305°C.