The invention discloses an energy-saving wall body material and a preparation method thereof. The energy-saving wall body material is prepared by mixing a wide-phase variable-temperature-region shaped phase-change material, cement, coal ash and a foaming agent in a mass ratio of 23 to 20 to 50 to 7, wherein the wide-phase variable-temperature-region shaped phase-change material is formed by mixing at least two different shaped phase-change materials, the shaped phase-change materials are formed by mixing carriers and core materials, and the core materials are organic phase-change materials. The preparation method comprises the following steps: diluting the foaming agent, and putting the foaming agent into a foaming machine for foaming, so as to obtain foam for later use; and putting the wide-phase variable-temperature-region shaped phase-change material, the cement and the coal ash into a stirring machine, uniformly stirring, sequentially adding water and foam, continuing to stir, so as to obtain formed slurry. The energy-saving wall body material is light in texture, high in compressive strength, poor in heat conduction capacity and low in drying shrinkage rate.