The invention provides a novel low-temperature composite chemical heat storage material and a preparation method thereof. The low-temperature composite chemical heat storage material is composed of high-energy-storage-density hydroxide hydrate as a composite chemical heat storage material matrix and a moisture absorption material, wherein the mass percent of the moisture absorption material is 5-40%. The preparation method comprises the following steps: heating the metal hydroxide hydrate and moisture absorption material, cooling, and carrying out mechanical grinding, common dissolution or ultrasonic dissolution, wherein the mass percent of the moisture absorption material is 10-40%; and drying, and screening according to the particle diameter of 63-125 mu m, thereby preparing the low-temperature composite chemical heat storage material. The composite chemical heat storage material solves the problem of overlow hydration reaction rate of the single active component; the compounding of the moisture absorption material greatly enhances the hydration rate of the hydroxide; and after the hydration reaction for 30 minutes, the energy storage density is obviously increased, and the circulating heat storage/release efficiency is obviously enhanced. The low-temperature composite chemical heat storage material has the advantages of stable heat storage and release reaction and long service life.