In order to study the influence of the water insulation property of the horizontal bottom sealing curtain on the environment around the foundation pit. Firstly, a field test is carried out to reveal the characteristics of groundwater seepage in highly permeable aquifers and the mechanism of land subsidence. Secondly, based on the groundwater seepage theory and the principle of effective stress, a three-dimensional fluid-solid coupling numerical model is established. Finally, the drawdown of groundwater and land subsidence caused by dewatering is simulated when the diaphragm wall is expended by 4 m, 8 m, and 12 m and the permeability of bottom sealing curtains is reduced to 2%, 5%, 10%, 15%, and 20% of the original stratum, respectively. And the impact of the bottom sealing dewatering on the foundation pit surrounding environment is revealed. The results show that: The bottom sealing can effectively control the land subsidence which is reduced by 68.48%~76.37%. When the permeability of bottom sealing curtains is reduced to less than 10% of the original stratum, the control effect of land subsidence is significant. Significant increasing the length of the diaphragm wall could also have a good effect on land subsidence control. However, it is necessary to analyze the feasibility of construction difficulty and cost.