Abstract:The coupling method of finite-infinite element is suggested to analyze the internal force and deformation of support structure for foundation pit. In order to simulate the actual situation,a new kind of interface element with thickness is installed in the interface between soil and structure. It is verified by a practical project that the new model can consider the space effect of deformation of retaining wall due to excavation and the time effect due to rheology of foundation. The deformation and internal force of support structure at any time and place can be calculated based on the program.