Nanocrystalline Mg2Ni-type alloys with nominal compositions of Mg20Ni10-xCux (x = 0, 1, 2, 3, 4, mass fraction, %) were synthesized by rapid quenching technique. The microstructures of the as-cast and quenched alloys were characterized by XRD, SEM and HRTEM. The electrochemical hydrogen storage performances were tested by an automatic galvanostatic system. The hydriding and dehydriding kinetics of the alloys were measured using an automatically controlled Sieverts apparatus. The results show that all the as-quenched alloys hold the typical nanocrystalline structure and the rapid quenching does not change the major phase Mg2Ni. The rapid quenching significantly improves the electrochemical hydrogen storage capacity of the alloys, whereas it slightly impairs the cycling stability of the alloys. Additionally, the hydrogen absorption and desorption capacities of the alloys significantly increase with rising quenching rate.