In order to improve the hydriding and dehydriding behaviour of the Mg2Ni-type alloys, Ni in the alloy was partially substituted by Co, and melt-spinning technology was used to prepare the Mg20Ni10-xCox (x=0, 1, 2, 3, 4) hydrogen storage alloys. The structures of the as-cast and spun alloys were studied by XRD, SEM and HRTEM. The hydriding and dehydriding kinetics as well as the electrochemical performances of the alloys were measured. The results show that no amorphous phase is detected in the as-spun Co-free alloy, but the as-spun alloys substituted by Co display the presence of an amorphous phase. The substitution of Co for Ni and the melt spinning significantly improve the hydrogen absorption and desorption performances of the as-cast and spun alloys. Meanwhile, the substitution of Co for Ni enhances the discharge capacity and cycle stability of the as-spun alloys dramatically.