Abstract: During the development of gas reservoirs with aquifers, reservoir pressure decreases gradually with gas production, and edge and bottom water will cone into gas reservoirs. In the early stage of water invasion, waterflood front is relatively far from bottom hole. If the aquifer is distributed uniformly, the waterflood front can advance stably, at the moment the driving effect of aquifer can replenish energy for gas reservoirs, allowing the average gas reservoir pressure drop to slow down and gas production to be maintained. In the middle-late stage of water invasion, gas wells will be watered out rapidly and wellbore liquid loading will seriously impact gas production. Therefore, the analysis of water invasion performance and obtaining of water invasion time, aquifer size and water influx at each time point are of great significance for developing gas reservoirs with aquifer. Iterative solution is made by combining material balance equation for water-drive gas reservoir and pseudo-steady state water invasion equation. Finally, by using C# programming language, parameters including dynamic reserves of gas reservoir, aquifer size, and water invasion rate and cumulative water influx at each time point can be determined on the basis of production data matching in gas wells. The established numerical simulation model for gas reservoirs verifies that the method is reliable and applicable in field, and can get results rapidly with small error. The numerical simulation results directly show the validity of the water influx evaluation