Abstract: As an important component of compressed air energy storage systems, the structural design and thermodynamic characteristics of artificial caverns play a crucial role in practical engineering construction. Based on Fluent simulation software, a three-dimensional dynamic simulation model of the tunnel type artificial cavern was established. Model independence verification was carried out, and the influence law of inflation port on the distribution of entropy production inside the cavern was obtained. Furthermore, an optimized structure was proposed to add a bent pipe at the end of the inflation port. Then the simulation of the optimized structure was conduced under a standard cycle operating condition. Results show that turbulent flow and fluid viscosity are the main causes of energy loss during the cavern inflation process. Increasing the diameter of the inflation port can reduce the entropy production inside the cavern. When the diameter of the inflation port is increased from 2.0 m to 3.5 m, the proportion of viscous entropy production increases from 47.29% to 53.03%, and the proportion of turbulent entropy production decreases from 52.68% to 46.68%. After structural optimization, the total entropy production of the cavern is reduced by 34.86%. During the process of inflation-gas storage-deflation-gas storage, the temperature and pressure inside the cavern show a rising-falling-falling-rising trend. The highest temperature inside the chamber is 331 K, achieving good temperature control effect.