Abstract: The temperature of the heat storage medium in the high-temperature molten salt storage tank is about 600 ℃, and the temperature drop is required to not exceed 1 ℃ per day. In order to meet the thermal insulation requirements, the foundation of the storage tank is often made of ceramsite as the thermal insulation material. Through the experimental study of the chemical composition, material properties and high temperature thermal parameters of five typical ceramsite under different grades, the key parameters such as physical and mechanical properties, phase change temperature, linear expansion coefficient, and thermal conductivity at different temperatures（20-600 ℃） are obtained, and the thermal conductivity and deformation mechanism of ceramsite are revealed, which provide guidance for the design of ceramic particles in the foundation of high temperature heat storage tanks.