Starting from the definition of porosity and introducing coefficient ofpore fluid compressibility, this paper, based on the principle of continuity ofgroundwater vadose field, has derived parameters for hydrologic logging, i. e.apparent resistivity, selfpotential and gamma-ray, and with these parametersformulated a mathematic model for calculating water supply of aquifer andwater-yield per well. The major factors affecting calculation lparameters ofthe model include eaponeatial law reflecting variation in movable water systemwith depth, effective porosity, lithologic characters and method as well asempirical formula for judging lithologic characters by logging, diameter ofwell and fall of water level. With sufficient practical data and using methodof the least square, we have determined the coefficient of the model anddesigned an integrated program for model calculation, thus opening up aneffective way for quantitative and microcomputerized calculation of hydrogeo-logic parameters through hydrologic logging system. The prognostic modelwill extend the application of hydrologic logging. The satisfactory resultsobtained demonstrate the correctness of the model and its great practicalvalue.