Abstract: The tightness and stability of compressed air energy storage (CAES) gas reservoir is the basis to ensure the safe operation of power station. There are many factors affecting the mechanics of gas reservoir and its mechanics characteristics are complex. The accurate prediction and evaluation of reliability and stability in the long-term operation process has always been an important topic. Based on the thermodynamic model of compressed air considering the leakage and heat transfer process as the unsteady boundary and the theory of heat-fluid-solid coupling as the core, this paper establishes a joint analysis model of gas storage under the coupling of multiple physical fields. The influence of groundwater in the rocks around the cave on the air tightness and stability of gas storage is studied. The results show that: (1) The existence of groundwater can reduce the gas loss per cycle in gas storage by 78%; (2) The lining is the main stress structure, which is mainly subjected to tensile stress, and the tensile stress at the top and bottom is concentrated, so it is necessary to pay attention to dense reinforcement; (3) The existence of groundwater can greatly reduce the effective stress of lining and the plastic zone area of surrounding rock. Therefore, groundwater can effectively assist sealing and is beneficial to the stability of lining surrounding rock structure.