The invention discloses a preparation method of high-quality aluminum trihydride. The preparation method comprises the following steps: sufficiently reacting the aluminum trihydride with organic amineand methylbenzene solvent under the protection of protective gas, performing suction-filtering and drying to obtain a solid product, namely the high-quality aluminum trihydride. The problem that thenormal aluminum trihydride is non-uniform in particle size distribution, serious in twining and crystal combination phenomenon, and more holes and cracks is solved, and the high-quality aluminum trihydride has better application prospect on the aspects of the solid propellant, the catalyst, the hydrogen storage material and the fuel battery and like.