The invention discloses a high-activity chemical chain hydrogen storage material and a preparation method thereof. The material is prepared by a solvothermal method. The preparation method comprises the following steps: firstly, dissolving FeCl2.4H2O, MgCl2.6H2O, AlCl3.6H2O and urea in methyl alcohol in a molar ratio of (1 to 3) : 1 : 1 : 7; performing solvothermal treatment on an obtained solution in an autoclave; drying an obtained product in vacuum to obtain the high-activity chemical chain hydrogen storage material with a layered double-metal hydroxide (LDH) structure. By adopting the high-activity chemical chain hydrogen storage material, a chemical chain cyclic oxidation hydrogen storage principle is adopted, hydrogen is indirectly stored by creating oxygen vacancies and inversely producing hydrogen on the oxygen vacancies, two hydrogen atoms are obtained theoretically through inversion on one oxygen vacancy, and the hydrogen storage density is twice that of conventional hydrogen storage at hydrogen vacancies. The material has a petal-shaped LDH structure and a large specific surface area, and more attachment sites are provided for Fe<2+>; under the adsorption action of a crystalline-state aluminum-containing laminate in the material, Mg<2+> and Fe<2+> are uniformly and stably distributed in the laminate, so that reactants can be in full contact with an active center, thereby greatly increasing the reaction activity of the material.