Magnesium (Mg)-based alloys have already been widely studied as the hydrogen storage materials because of their high reversible hydrogen storage capacity,low cost,light weight,etc.However,the poor de/hydrogenation kinetic properties dramatically hinder the practical applications.In this work,the MgH2-ANi5 (A =Ce,Nd,Pr,Sm,and Y) composites were prepared by a high-energy ball milling method,which can effectively refine the particle size thus improving the kinetic properties.Experimental results reveal that the MgH2-ANi5 composites mainly consist of Mg2NiH4,MgH2 and rare earth (RE) hydride,which will be dehydrogenated to form Mg2Ni,Mg and stable RE hydride reversibly.Accordingly,the as-milled MgH2-ANi5 (A =Ce,Nd,Pr,Sm,and Y) composites with various A-elements can respectively contribute to a reversible hydrogen storage capacity of 6.16 wt％,5.7 wt％,6.21 wt％,6.38 wt％,and 6.5 wt％at a temperature of 300 ℃,and show much better kinetic properties in comparison to the pure MgH2 without any additive.ln-situ formed Mg2Ni and stable RE hydride (such as CeH2.73 and YH2) might act as effective catalysts to significantly improve the hydrogen storage properties of MgH2.The present work provides a guideline on improving the kinetic properties of the Mg-based hydrogen storage alloys.