SiO2-based phase change and humidity storage composite materials with phase change thermal control performance and humidity storage humidity control performance were made with SiO2 as the carrier and fatty acid as a phase change material. Phase change thermal control performance and humidity storage humidity control performance of SiO2-based phase change and humidity storage composite materials with different fatty acid content were tested with isothermal sorption method and cooling curve method. Composition structure of SiO2-based phase change and humidity storage composite materials were tested by Fourier transform infrared spectrum to analyze chimeric mechanism of SiO2 and fatty acid. Characteristic FTIR absorption peaks of SiO2-based phase change and humidity storage composite materials were considered as input layer; different fatty acid content of SiO2-based phase change and humidity storage composite materials, average values of absorption equilibrium moisture content and desorption equilibrium moisture content of SiO2-based phase change and humidity storage composite materials with relative humidity as 52.89%, and cooling time from 30 to 15 ℃ of SiO2-based phase change and humidity storage composite materials were seen as output layer respectively; S activation function was treated as hidden layer; then, optimization performance forecast model of SiO2-based phase change and humidity storage composite materials with structural parameters and phase change and humidity storage comprehensive performance was established by back-propagation neural network. The results showed that SiO2 and fatty acid are only physical chimeric to each other, while there is no chemical reaction between them. SiO2-based phase change and humidity storage composite materials by adding in 0.079 mol fatty acid has the best phase change and humidity storage comprehensive performance, that is, absorption equilibrium moisture content is 0.132 3 g·g-1, desorption equilibrium moisture content is 0.147 5 g·g-1, average value of equilibrium moisture content is 0.139 9 g·g-1 when relative humidity is 52.89%, cooling time from 30 to 15 ℃ is 1 305 s. Optimization performance forecast model of SiO2-based phase change and humidity storage composite materials are proved well with good accuracy, and the relative error of predicted data and experimental data are -2.07% and 2.45%, respectively; forecast model can be used for optimizing forecast phase change thermal control performance and humidity storage humidity control performance of SiO2-based phase change and humidity storage composite materials.