Abstract: Compressed air energy storage is a long-duration energy storage technology that solves the volatility problem of renewable energy. It is of great significance to study the characteristics of variable operating conditions and the optimization of operation modes for the scientific regulation and control of compressed air energy storage. A 10 MW compressed air energy storage system was taken as the research object, a modular modeling method was used to establish simulation models of the energy storage process and energy release process of the compressed air energy storage system based on Modelica language, and the operation modes of the system under different working conditions were optimized based on the particle swarm optimization algorithm. Results show that the established compressed air energy storage system model can accurately simulate the operation processes of energy storage and energy release, and have good results when applied to the optimization of operation strategies under different working conditions of the system. The optimization of variable operating conditions can significantly reduce the power consumption of energy storage and air consumption of energy release, and improve the round-trip efficiency of the system. The study results can support the analysis of the characteristics of variable operating conditions and the optimization of operation strategies of compressed air energy storage system.