Abstract: A magnesium-based solid hydrogen storage material with liquid phase regulation function and a preparation method thereof and an application thereof in an all-solid-state battery are provided, belonging to the technical field of new energy. The magnesium-based solid hydrogen storage material with the liquid phase regulation function includes following raw materials in percentage by mass: 95% of magnesium hydride and 5% of lithium borohydride. Lithium borohydride as an ionic conductor is dispersed on a surface and matrix of magnesium hydride, which provides channels for the rapid hydrogen storage of the magnesium hydride-based materials.