Abstract: Diaphragm wall and internal support are commonly used forms of support for foundation pit engineering. The deformation of the foundation pit is generally considered during the excavation of the foundation pit, while the deformation in the stage of support removal is ignored. Based on the Shenzhen Vanke Coastal Foundation Pit Project, this paper mainly studies the impact of excavation and support removal of a foundation pit on the surrounding environment by finite element numerical simulation. The following conclusions are obtained. The deformation law of the support removal and the excavation is consistent, and it is obviously influenced by space-time effect. The amounts of deformation in the two stages are similar, and the sum of the deformation amounts accounts for more than 85% of the total deformation. The deformation of the bottom soil excavation and bottom support removal is the biggest. The reasons are as follows: firstly, the three supports are not equidistant, and the thickness of the bottom soil is large; Secondly, the thickness of granite residual soil varies greatly. Finally, after the support is removed, only the basement floor is provided with a change brace, which causes the cantilever section of the pile body to be long. The simulation results show that the lateral displacement at the top of the foundation pit, ground settlement and building settlement are basically consistent with the monitoring data. The results can provide reference for similar projects.