Abstract: Stearic acid/SiO₂ form-stable phase change material (PCM) was synthesized by sol-gel process under ultrasound assisted. Stearic acid acted as latent heat storage material, tetraethyl orthosilicate (TEOS) acted as silica precursor. In order to research the preparation process of the form-stable PCM, the sol-gel processes assisted by different ultrasound power and different kinds of catalyst were analyzed. At last, the maximum stearic acid loading mass fraction of hybrid PCMs with good form-stable character was found to be 60%. The formation process of stearic acid/SiO₂ PCM has many advantages such as the whole process without any solvent or surfactant, fast gel formation and convenient preparation. The structure and thermal performance of stearic acid/SiO₂ form-stable PCM were analyzed by FTIR, DSC and TG. The results show that the latent heat of stearic acid/SiO₂ form-stable PCM is 91.46 J/g, and this material has a good thermal stability below 175℃.