Watering out of gas wells influences the deliverability of gas wells and the recovery of gas reservoirs severely. During the development of gas reservoirs, it is  key to identify early water influx for producing without water and developing actively. Presently, there are many methods such as water monitoring, pressure  monitoring, well test and so on. In this paper, the applicability of the methods is presented respectively: the method of water monitoring can be used only after  producing water of gas well, the method of P/Zplot is used at the stage of nonlinear relationship between P/Z  and cumulative gas production, the methods  of well test can be used with abundance well test data, water influx calculation has its uncertainty. And then, it is given that analyzing all information on  water invasion synthetically is the only way to reducing the risk of identifying early water influx of gas reservoirs based on its complexity and the  applicability of the methods.