Abstract: Ground manifold is an important part of Compressed Air Energy Storage (CAES) system. Aiming at the technical characteristics of compressed air pipeline system outside the factory of 300MW salt cavern compressed air energy storage power station in Feicheng, Shandong Province, such as frequent start and stop, fast response and high safety requirements, the engineering problems such as fatigue life and fatigue damage accumulation of pipe fittings under alternating stress are analyzed. Taking three typical structural units such as tee pipe, reducer pipe and 90° elbow pipe as objects,based on the principle of improving the service life of pipe fittings, the structural parameter optimization and combination scheme design are carried out. The dynamic characteristics of the pipe under periodic alternating load and the safety analysis in the life cycle are studied by means of fluid-solid coupling. The analysis results show that: (1) Under the action of design pressure, when the safety factor is 2, the fatigue life of the optimized tee pipe, reducer pipe and elbow pipe is 46362.5 times, 41747 times and 50725 times respectively, which meets the fatigue life requirement of 40,000 times of stable energy storage and release. (2) Under the action of cyclic alternating load, the fatigue life of the three typical structural units under the fluid-solid coupling dynamic characteristics is 40870,40295.5 and 44643.5 times, respectively, which meets the service life and safety performance requirements. (3) When designing and optimizing the structure of pipe fittings in the 300 MW salt cavern compressed air energy storage system, constraints can be applied to the tee in the X and Y directions, to the reducer in the X direction, and to the elbow in the X and Z directions, so as to better reduce the vibration of the pipe fittings.The above analysis work provides technical support for the safe operation of the ground manifold of the 300MW compressed air energy storage system.