The invention discloses a solar inorganic energy storage material and a preparation method thereof, the solar inorganic energy storage material comprises the following raw materials by weight: 28-32 parts of anhydrous magnesium chloride, 18-21 parts of anhydrous calcium chloride, 50 parts of water, 10 parts of aluminum hydroxide, 5 parts of iron oxide, 5 parts of zinc oxide, 80 parts of phosphoric acid, 1 part of alumina, 1 part of calcium oxide, and 1 part of silica. The solar inorganic energy storage material disclosed by the invention is low in cost, high in enthalpy value and low in heat conductivity coefficient, belongs to an efficient thermal-insulation energy-saving material, has the enthalpy value of 3,500 J/g and the phase transition temperature of 25 +/-3 DEG C, is waterproof and fireproof, and has the heat conductivity coefficient of 0.0119 W/(m.k). The solar inorganic energy storage material has wide application prospects in the fields of solar heat utilization, waste heat recovery, electric power peak load shifting, heat management systems, building energy conservation and the like, has the characteristics of high latent heat storage density, no supercooling or superheating and the like, and shows wide application prospects in the field of clean energy application.