Taking a foundation pit project in Wuhan as the background， based on two observation indicators of water level drop inside and outside the confined layer pit and surface settlement outside the pit， a three-dimensional numerical calculation model for group well precipitation was established using finite element software ABAQUS for numerical simulation analysis. By setting multiple calculation conditions， under the conditions of different insertion ratios of suspended waterproof curtains λ， the influence of different well screen lengths L and filter tube burial depth H on the water level drop inside and outside the confined layer pit and surface settlement outside the pit was studied. The research results indicate that the impact of the insertion ratio λ on the water leverl drops inside and outside the confined layer pit and the surface settlement outside the pit is much greater than that of the length L and burial depth H of the well screen in the dewatering well. When the λ is between 0.4 and 0.6， there is a large space to increase the water level drop inside the confined layer pit or decrease the water level drop outside the confined layer pit by changing the length L and the burial depth H. When λ exceeds 0.6， it has a good water blocking effect. The buried depth H of the well screen should be located at the top of the confined aquifer， and the length of the well screen L should not exceed 0.4 times the thickness of the confined aquifer M.