According to the research achievements of phase change and humidity storage composite materials preparation in early stage, SiO2-based phase change and humidity storage composite materials were made by sol-gel method with SiO2 as the carrier and decanoic acid-palmitic acid as a phase change material in this paper. Synthetic materials in every stage of preparation process of decanoic acid-palmitic acid/SiO2 phase change and humidity storage composite materials were measured by Fourier transform infrared spectrum, such as phase change material preparation stage, SiO2 carrier material preparation stage and decanoic acid-palmitic acid/SiO2 phase change and humidity storage composite materials preparation stage. In the process of decanoic acid-palmitic acid/SiO2 phase change and humidity storage composite materials preparation, SiO2 network structure forming mechanism, decanoic acid-palmitic acid embed mode, chimeric mechanism of SiO2 and decanoic acid-palmitic acid were researched, respectively, in order to explain the mechanism of how to prepare decanoic acid-palmitic acid/SiO2 phase change and humidity storage composite materials by sol-gel method. Meanwhile, material composition and micro topography of decanoic acid-palmitic acid/SiO2 phase change and humidity storage composite materials were tested by X-ray diffracmeter and scanning electron microscope, so as to provide evidence about preparation mechanism of decanoic acid-palmitic acid/SiO2 phase change and humidity storage composite materials. The results showed that decanoic acid-palmitic acid is packed in a large number of closed pores or cages which were formed through breaking and restructuring of Si—O—Si groups; then, decanoic acid-palmitic acid/SiO2 phase change and humidity storage composite materials can be prepared based on those mentioned above. Decanoic acid-palmitic acid and SiO2 are only physical chimeric to each other, without any chemical reaction in the preparation process of decanoic acid-palmitic acid/SiO2 phase change and humidity storage composite materials. A large number of closed pores or cages are formed by SiO2 in acid-palmitic acid/SiO2 phase change and humidity storage composite materials, of which one part is used for coating decanoic acid-palmitic acid with phase change thermal control performance, and the other part is used for network space structure with humidity storage humidity control performance, in order to achieve the purpose of adjusting indoor temperature and humidity at the same time.