To investigate the effect of Nb on the dehydrogenation properties of Mg-Nb composite films,Mg/Nb eightlayer film and Mg-10 at% Nb alloy film with the similar Mgto-Nb atomic ratio were prepared by magnetron sputtering.Results show that both Mg/Nb eight-layer film and Mg-10 at% Nb alloy film exhibit excellent de/hydrogenation properties.Mg-10 at% Nb alloy film starts to release hydrogen at 108 ℃,and its desorption peak temperature is lower to 146 ℃,which is much better than that of pure MgH_2 under the same condition.Scanning electron microscopy(SEM) results demonstrate that the dispersive Nb nanoparticles in Mg/Nb eightlayer film may serve as nucleation sites for MgMgH_2 reactions,which can provide channels for H diffusion.For Mg-10 at% Nb alloy film,the uniform distributions of Nb can accelerate the hydrogen diffusion and effectively improve the dehydrogenation kinetics for MgH_2.This study provides an enlightening way for designing and preparing Mg-based composite films with excellent dehydrogenation properties. To investigate the effect of Nb on the dehydrogenation properties of Mg-Nb composite films, Mg / Nb eightlayer film and Mg-10 at% Nb alloy film with similar Mgto-Nb atomic ratios were prepared by magnetron sputtering. Results show that both Mg / Nb eight-layer film and Mg-10 at% Nb alloy film exhibit excellent de / hydrogenation properties. Mg-10 at% Nb alloy film starts to release hydrogen at 108 ° C, and its desorption peak temperature is lower to 146 ° C, which is much better than that of pure MgH_2 under the same condition. Scanning electron microscopy (SEM) demonstrated demonstrates that the dispersive Nb nanoparticles in Mg / Nb eightlayer film may serve as nucleation sites for MgMgH_2 reactions, which can provide channels for H diffusion .For Mg-10 at% Nb alloy film, the uniform distributions of Nb can accelerate the hydrogen diffusion and effectively improve the dehydrogenation kinetics for MgH_2.This study provides an enlightening way for designing and preparing Mg-based composite films with ex clentlent dehydrogenation properties.