Abstract: Average formation pressure is a fundamental parameter for productivity evaluation and dynamic analysis. To accurately and rapidly acquire the average formation pressure is of great significance to the efficient development of gas reservoirs. This paper analyzes the change rule of average formation pressure based on its variation with time. The research shows that the equivalent point of average formation pressure only changes with time, and the decline rate of average formation pressure is equal to or approximately equal to that of bottom-hole flow pressure. According to the material balance equation of a closed elastically-driven gas reservoir, considering the variation of the deviation coefficient and bottom hole flow pressure with the average formation pressure, this paper derives and establishes a new method for tracking and calculating the average formation pressure, which can be iteratively calculated by substituting the production data. Method verification shows that gas production rate and recovery percent together affect the calculation results. Application examples show that there is a small relative error between the tracking calculation method and the pressure buildup test and material balance method, thus meeting the accuracy requirements for engineering calculation, and the tracking calculation method is really independent of production test data, which saves test costs and avoids the impact of tests on production.