In order to explore what kind of internal support layout can ensure the safety and stability of adjacent existing buildings and long strip deep foundation pit under sensitive environment, taking the actual project as the background, Midas GTS NX is used to analyze the three-dimensional interaction of soil and structure in foundation pit, the deformation control indexes of the building and foundation pit under various types of internal support are compared, and compared with the monitoring alarm value and field monitoring data. The results showed that: internal support of opposite brace and angle brace type is more suitable than other types; the layout of the inner support has a significant effect on the change of the basement uplift, but has little effect on the amount of the uplift; it is suggested to increase the stiffness at the weak point when using the corner brace type and the double circular ring beam type inner support. The proposed internal bracing can not only ensure the safety of foundation pit, but also better control the deformation of adjacent existing buildings, which has certain reference value for the design, construction and deformation control of similar projects.