Abstract: Based on analyzing the discharge of the partially penetrated wells in phreatic aquifer,introducing the conception of "the effective zone" of pumping,probing into the feasibility and comparative error by translating the calculation of the discharge of the partially penetrated wells into the calculation of the discharge of the equivalent completely penetrated wells.Several examples indicate that simplified method can control the comparative error of the discharge of one pit within 20percent,then prove that the simplified method to a certainly has practical value.