The invention provides a method for decreasing the hydrogen desorption temperature of aluminum hydride through a rare earth oxide, and belongs to the field of hydrogen-storage materials. The expression of a hydrogen-storage material is AlH<3+x> mol%MO, wherein x is greater than 0.1 and less than 3, M is at least one or two or more of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Yand Sc, m is the stoichiometric ratio of M in the molecular formula MO, and m is equal to 1 or 2; and n is the stoichiometric ratio of O in the molecular formula, and n is equal to 2 or 3. The invention further provides a preparation method of the rare earth oxide doped aluminum hydride hydrogen-storage material, and the method comprises the steps that a hydride and the rare earth oxide areput into a ball milling tank to be subjected to mechanical ball milling, the weight ratio of a ball material is (10 to 100):1, and the ball milling time is 0.1-10 h. The preparation method of the prepared rare earth oxide doped aluminum hydride hydrogen-storage material is simple in technological process, easy to control, good in controllability and low in catalyst cost.