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Background. In order to make up for the defect that a single phase change material cannot meet the phase change temperature in a specific application field, three kinds of materials with higher phase change temperature are selected in this paper. Through the phase change material composite method, it was adopted to carry out step cooling curve test and differential scanning calorimetry (DSC) test, based on the second law of thermodynamics and the theory of phase equilibrium. DSC thermal analysis and Fourier transform infrared spectroscopy (FT-IR) characterization were carried out. The phase change diatomite was used for packaging materials and durability evaluation. The results show that when TD-MA : LA = 6.2 : 3.8, the phase transition temperature of the experimental ternary composite phase change material is 20.1°C. The adsorption of diatomite to phase change material (PCM) is only physical adsorption, and the thermal stability is good after 100 phase change cycles. The maximum mass loss rate of phase change diatomite encapsulated by phenylpropene emulsion and cement powder is only 0.65%, at last, this phase change diatomite is suitable for building envelope structure.