Abstract: The traditional method of foundation pit demonstration is on the two-dimensional map, experts need to do a lot of preliminary works before the demonstration, this brings many problems like time-consuming, low efficiency and difficulties to archive and access after the completion of the project. In order to solve the problems, a series of methods by using 3D GIS technology to support foundation pit scheme argumentation are put forward, including the technology of data collection and database building for 3D spatial geo-information around the project, the technology of constructing 3D geological environment by optimizing the spatial interpolation algorithm, the technology of deformation monitoring and 3D deformation simulation for foundation pit, etc., so as to assist the scheme demonstration and decision-making for the foundation pit construction. Combined with the foundation pit project of Hongqi South Road Station on metro Line 6 in Tianjin City, the 3DGIS technology is verified to have outstanding performance.