NOVELTY - A composite thermal storage phase-change material comprises sodium sulfate decahydrate, sodium carbonate, borax, polycarboxylic acid, and water. When ambient temperature rises to over 32 degrees C, sodium sulfate decahydrate absorbs heat in the form of melting heat, and melts into sodium sulfate and water within 10 minutes. When ambient temperature drops to less than 32 degrees C, sodium sulfate and water recombine into sodium sulfate crystals and heat is released as crystallization heat. Thus, temperature is adjusted and day-night temperature difference is reduced.    USE - Composite thermal storage phase-change material is used for heat accumulation and shielding, and solar constant-temperature bricks (all claimed) used in office buildings and daily domestic warming.    ADVANTAGE - The composite thermal storage phase-change material has high phase-change heat capacity, high heat conductivity, and excellent stability, economical efficiency, and durability. The material can be used in high altitudes, polar regions, oceanic regions, deserts, plateau, and mountainous regions. The phase-change material can be manufactured by a simple and easy method.    DETAILED DESCRIPTION - A composite thermal storage phase-change material comprises a heat storage agent, a phase-change temperature regulator, a nucleating agent, a suspension thickener, and a solvent. The heat storage agent, phase-change temperature regulator, nucleating agent, suspension thickener, and solvent are pure sodium sulfate decahydrate, pure sodium carbonate, pure borax, polycarboxylic acid, and water, respectively. The composite material comprises (in wt.%) pure sodium sulfate (38), pure sodium carbonate (8), pure borax (3), polycarboxylic acid (2), and water (49). When the outside ambient temperature rises to over 32 degrees C, the heat storage agent absorbs heat in the form of melting heat, and melts into sodium sulfate and water within 10 minutes. When the outside ambient temperature drops to less than 32 degrees C, sodium sulfate and water in the solution recombine into crystal sodium sulfate decahydrate and heat is released in the form of crystallization heat. Thus, temperature is adjusted and the day-and-night temperature difference is reduced.