This invention discloses a composite catalyst for improving the hydrogen storage performance of magnesiumhydride and its preparation method, belonging to the field of hydrogen storage materials technology. The catalyst is composed of Ni, NiOOH, and TiO2 nanocrystals, as well as amorphous carbon, with the amorphous carboncoating the surface of a Ni / NiOOH / TiO2 heterojunction matrix, forming a core-shell structure. Its preparation includes the following steps: First, nickel, titanium, and aluminum are melted into a nickel-titanium-aluminum alloy, and then subjected to corrosion activation treatment with sodiumhydroxide solution to obtain porous nickel-titaniumsolid solution powder; then, the porous nickel-titanium solid solution powder is added to deionized water along with glucose and subjected to hydrothermal treatment; finally, the hydrothermal treatment product is filtered, washed, and dried to obtain the target product. Mechanically mixing the prepared Ni / NiOOH / TiO2@C catalyst with MgH2 can improve the hydrogen storage performance of MgH2. The composite catalyst provided by this invention has widely available raw materials and a simple preparation process; using it as a catalyst for hydrogen storage in MgH2 can significantly reduce the hydrogen desorption temperature of MgH2 and improve cycle stability.