The three-dimensional finite element analysis (3D FEA) of support system is carried out with the help of ABAQUS. It is about the internal force and deformation of a typical deep foundation pit during the foundational construction at Tianjin Economical Development Area (TEDA)

which is famous for its soft ground. The method of active and inactive element can simulate the excavation progress better; and also solid elements for soil and support system are employed in order to reduce the error produced by degree-of-freedom coupling of different kinds of elements. By comparing the internal force and deformation of the support system of theoretical analysis with the results of field monitoring

it shows that the accuracy of 3D FEA is sufficient for theoretical analysis. The method and conclusions are useful for other similar projects of design and construction of deep foundation pit on soft ground.