The judgment of the aquifer activity level and the recovery of waterdrive gas reservoir are intricate and crucial. The paper is to develop a new criterion to determine the aquifer activity level and a new chart method demarcating the range of recovery variation. In the first place, reasoning and defining the new criterion of the determinate aquifer activity level is obtained by water influx coefficient B, based on the material balance equation of water drive gas reservoirs and the study of previous scholars. Thus a theoretical curve equation and a suppositional curve equation are derived and defined. The former one is pr(1-RgB)=1-Rg, which shows the relationship between the relative pressure pr and the degree of reserve recovery value Rg with different B. The latter one, pra=(1-ER)/(1-aEva)(where a=Sgr/Sgi), relates to the ratio of residual gas saturation and original gas saturation Sgr/Sgi, the ultimate volumetric sweep efficiency Eva and represents the relation between the relative abandonment pressure pra and the recovery ER. Finally, a set of charts is established by the two equations, by which we can set up a table to determine the variation range of the recovery with corresponding Sgr/Sgi value and Eva value when the aquifer is at different activity level.

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