Abstract: In order to avoid the water disaster of fault and sandstone below the coal seam, it is necessary to master the conductivity of fault accurately. Through the dewatering test with large drawdown and water flow of Baotashan sandstone aquifer in the bottom of Yan’an Formation, the good conductivity of DF₂₀ fault in vertical was found out, and the DF₂₀ fault is an important hydraulic connection channel of each aquifer. It is clear that DF₂₀ and F₂ fault have hydraulic connection in horizontal direction, and Triassic aquifer has the hydraulic connetion with Baotashan sandstone aquifer by DF20 and F₂ faults. It is proposed that the intersection of DF₂₀ and FD₅ faults has the strongest conductivity and is the main location of water exchange of each aquifer. The conductivity of DF₂₀ fault is not uniform in the horizontal direction. The conductivity of DF₂₀ fault located in the middle of the coal field is weak, while the conductivity of DF₂₀ fault in the south of the coal field is strong. The results show that the hydrogeological parameters of the fault not only can be obtained through the pumping test and dewatering test, but also the hydrogeological conductivity and spatial characteristics of the fault can be found out.