Abstract: A numerical method considering the fluid-mechanical interaction is used to study the wall deformation and the ground settlements caused by dewatering in a confined aquifer in deep excavation. In the simulation of project example, the fluid-mechanical interaction methods based on the Biot’s consolidation theory are used to calculate the variation of settlements in deep excavation. Mechanics and seepage are iterated alternately to solve the deformation under combined effect of unloading and dewatering. The rationality of this method is verified by comparing with observed data. The three-dimensional numerical models of deep excavation are established. And the situations with or without dewatering are made direct comparison in terms of dewatering-induced wall deformations and ground surface settlements. By stripping the correlation curve of dewatering-induced additional settlements outside the pit, this paper focus on its discrepancies and mechanism with the comparison of one-dimensional consolidation theory based on the same pore pressure change. The results show that dewatering in the confined aquifer has less effects on wall deformation, but intensifies the magnitude and the influence range of total ground surface settlements. The dewatering-induced additional ground surface settlements outside 1.5 times of excavation depth of the pit match well with the settlements of one-dimensional consolidation theory, while the settlements discrepancy within 1.5 times of excavation depth behind the wall is mainly attributed to the soil-wall interaction.