Abstract: The heat storage performance and phase change stability of mixed phase-change materials consisted of stearic acid and Na₂HPO₄·12H₂O was studied by means of Fourier transformation infrared spectrum analyses and DSC.The specific heat capacity of mixed materials was also determined experimentally.The results show that all absorption peaks of the functional groups and chemical bonds of stearic acid still exist, which suggests that stearic acid and Na₂HPO₄·12H₂O crystal materials have good phase change stability and chemical compatibility.Mixtures of these two materials can overcome the disadvantage of both the sub cooling of Na₂HPO₄·12H₂O and the low specific heat capacity of stearic acid in order to complement each other on the basis of organic/inorganic characteristics.