A eutectic hydrate salt (EHS) with low supercooling degree and no phase separation was prepared using decahydrate sodium carbonate (SCD) and dodecahydrate sodium hydrogen phosphate (DHPD) as the main phase-change materials. Adding nonahydrate sodium silicate as a nucleating agent. A shape-stabled phase-change material (SSPCM) of the fixed EHS/SiO₂ was prepared by adsorbing EHS on gas-phase SiO₂ with impregnation method. The transition temperature of SSPCM was 24.08 ℃, the enthalpy value was 146.6 J/g, the supercooling degree was 0.55 ℃ and the thermal conductivity was 0.5454 W/m?K. Compared with insulation foam, the SSPCM extended the warming time of the central temperature in the building by 3.26 times and the cooling time by 1.39 times, showing excellent"thermal buffering", which have broad application prospects in building energy efficiency.