During the cyclic gas injection of gas condensate reservoir with bottom or edge water, complicate phase changes and energy conversion take place. A new calculation model for condensate oil saturation is established based on the principle of volume conservation. Moreover, the calculation model considers the influencing factors such as retrograde condensation, connate water evaporation, elastic expansion of reservoir rocks, and external dynamic water invasion. Combining the reservoir fluid property and dynamic production data, this model can calculate the condensate oil saturation under different reservoir pressures quickly. The Case study shows that the condensate oil saturation obtained by this model coincides with the indoor depletion experiment and reservoir numerical simulation. Meanwhile, the sensitivity evaluation of the above influencing factors is carried out. Furthermore, the factors impacting the calculated results from high to low are external dynamic water invasion, elastic expansion of reservoir rocks and connate water evaporation.