The effect of metal scandium (Sc) on the hydrogen-storage properties of the magnesium-nickel (Mg2Ni) alloy has been explored using the ultrasoft pseudopotential approach, rooted in the principles of Density Functional Theory (DFT). The binding energy, lattice constant, enthalpy of formation, standard enthalpy of reaction, charge density, density of states and bond order for the Mg2-xScxNi (x = 0, 0.25, 0.5, 1) alloys and their hydrides were calculated. Furthermore, the analysis of the atomic bonding and the structural stability of Mg2-xScxNi and hydrides were also facilitated. The results show that the preference site of the Sc atom in Mg2-xScxNi (x = 0, 0.25, 0.5, 1) alloys is Mg (6i) under the condition of a Sc doping concentration of 0.25. This causes a decrease in the stability of the Mg1.75Sc0.25Ni alloy. Moreover, the addition of Sc to Mg2-xScxNiH4 weakens the interaction of H-Ni and H-Mg, thereby facilitating the hydrogen-release reaction and effectively enhancing the hydrogen-release capability of Mg2-xScxNiH4.