The nanocrystalline Mg2Ni-type alloys with nominal compositions of Mg20Ni10-xCux (x = 0-4) are synthesized by melt-spinning technique. The microstructures of the as-cast and spun alloys are characterized by XRD, SEM and HRTEM. The hydrogen absorption and desorption kinetics of the alloys are measured using an automatically controlled Sieverts apparatus. The electrochemical performances are tested by an automatic galvanostatic system. The results show that all the as-spun alloys hold typical nanocrystalline structure. The substitution of Cu for Ni does not change the major phase Mg2Ni. The hydrogen absorption capacity of the alloys first increases and then decreases with rising Cu content, but the hydrogen desorption capacity of the alloys always grows with increasing Cu content. Furthermore, the substitution of Cu for Ni significantly improves the electrochemical hydrogen storage performances of the alloys, involving both the discharge capacity and the electrochemical cycle stability. (C) 2010 Elsevier B.V. All rights reserved.