Abstract: In order to obtain the parameter configuration of storage tank in pumped hydro combined with compressed air energy storage system（PHCA） with high energy density and energy storage efficiency in actual operation, in this paper, the thermodynamic modeling of the energy storage tank system in the system was carried out, and the influence laws of its pressure configuration, heat exchange conditions and flow configuration on the efficiency and energy density of the energy storage tank system were analyzed. The results showed that: For the rated storage pressure, there is always an optimal initial pressure corresponding to it, which can make the energy density reach the maximum.The ratio between the optimal initial pressure and the storage pressure is between 2 and 3, and the storage efficiency of the corresponding pressure configuration is stable between 92% and 93%. When the heat transfer coefficient and storage time are in a certain configuration range, the system will fall into the low efficiency zone. In the design of storage tank, the heat transfer capacity should be evaluated to avoid the low efficiency zone. During operation, the storage time has a great impact on the energy storage efficiency, and choosing the suitable working flow of pump turbine can ensure efficiency. When the storage time is short, the configuration method adopted is high compression flow and high expansion flow. When the storage time becomes longer, the compression and expansion flow should be reduced at the same time. The research results can provide a theoretical basis for the design and operation of the system.