Abstract: The development mode of underground space in modern cities is changing from independent space and single function to a comprehensive one of regional connectivity. The depth and area of foundation pits increase, showing the characteristics of regional centralized development. Due to many conditions, many large-scale projects are usually implemented in phases and blocks. After setting up soil (buffer) between them, the adjacent foundation pits can be excavated simultaneously. The synchronous excavation will greatly save the construction period and facilitate the deformation control of the enclosure. Numerical simulation methods are mainly used, and the background engineering is used as the basic model to analyze the force and deformation trends of the enclosure with different buffer widths. On this basis, a reasonable buffer width range for the synchronous excavation of the adjacent foundation pits in Shanghai area is proposed. At the same time, combined with engineering examples, the influence of construction overload on the simultaneous excavation of adjacent foundation pits is analyzed.