In this study, melting and casting of Mg-Ni alloys in ambient atmosphere for mass production, nickel content adjustment for enhancing hydrogen capacity and reducing alloy weight, and cyclic hydriding/dehydriding test for evaluation of degradation properties were investigated. Mg-Ni alloys were fabricated by Rotation-Cylinder Method (RCM) in ambient atmosphere. Hydriding/dehydriding reactions were repeated 350 times at 350°C to evaluate degradation property. SEM-EDS analysis revealed that the lamellar eutectic structure of Mg-Ni alloy consists of Mg-rich α-phase and β-Mg2Ni. It is supposed that the lamellar eutectic structure enhances hydrogenation properties of Mg-Ni alloys.