Abstract: During the multi-period expansion after the underground gas storage (UGS) rebuilt from condensate gas reservoir with edge water is put into operation, the production in the stage of gas production is not in accordance with the upper and lower limit pressure due to the demand of seasonal peak shaving. In addition, it is difficult to calculate the parameters of UGS working gas volume because of the complex gas/water relationship and the change of condensate gas phase state. In this paper, the material balance equation of edge-water condensate gas reservoir UGS was deduced according to the principle of material balance. In this equation, edge water incursion, condensate gas phase change and rock compressibility are considered. Then, the method for calculating the multi-cycle working gas volume of edge-water condensate gas reservoir UGS was established by calculating the available gas pore volume of each injection/production cycle. Finally, the calculation method was validated by conducting case study on one domestic UGS. It is shown that the working gas volume calculated by this model is in accordance with the actual volume. This method improves the calculation accuracy of UGS working gas volume and provides the technical support for multi-cycle inventory verification and efficient UGS operation management.