Abstract: Sodium acetate trihydrate (SAT), which has high energy storage density and high thermal conductivity, is an important phase change material (PCM) for thermal storage. But it suffers from serious supercooling during the solidification process, which constrains its application. In this study, seven kinds of nucleating agents (Na₂HPO₄12H₂O, Na₂CO₃10H₂O, Na₄P₂O₇10H₂O, Na₃PO₄12H₂O, Na₂SiO₃9H₂O, Na₂S₂O₃9H₂O and Na₂B₄O₇10H₂O) were proposed to reduce the degree of supercooling of SAT. With the help of the high-low temperature test chamber, the experiments were performed to investigate the degree of supercoiling, and to validate the thermal stability of composite PCM by using the curve law of step. As a result, the composite PCM with the mass fraction of 96%CH₃COONa3H₂O+2%Na₂HPO₄12H₂O+2% carboxymethycellulose presents the smallest the degree of supercooling, which is 5.6℃. Moreover, the phase transformation point of the composite PCM varies a little with 25, 50 and 75 thermal cycles. While its latent heat would decrease and the degree of supercooling would increase with the number of thermal cycles increasing. Therefore, this study enriches the adjustment program of the degree of supercooling of SAT, and will be evaluated for engineering application in future offerings.