To improve the hydrogenation properties of Mg-Ni-base alloys, Mg-Ni/MmM(5) multi-layer film was fabricated by magnetron sputtering. The microstructure and hydrogenation properties of as-deposited film were characterized by X-ray diffraction, scanning electron microscopy and pressure-composition isotherm measurement. It was shown that the Mg-Ni layer is composed of preferred orientational nanocrystalline Mg2Ni and fine-crystalline Mg, while the MmM(5) layer is in amorphous structure. PCI curve of Mg-Ni/MmM(5) multi-layer film at 523 K is composed of two plateaus, which correspond to the bydriding and dehydriding reactions of Mg and Mg2Ni, respectively; A maximum hydrogen absorption content of 5.0 mass% is obtained at 523 K. The hydrogenation properties of Mg-Ni/MmM(5) multi-layer film are greatly improved than that of the corresponding Mg-Ni alloy target, which is attributed to the nanocrystalline structure of the Mg-Ni layer and catalytic role of the amorphous MmM(5) layer. However, the hydrogenation properties of Mg-Ni/MmM(5) multi-layer film are deteriorated after several cycles. (C) 2004 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.