The stress field of soils will change and bottom of foundation pit will upheave with excavation unloading. According to the relation between deformation and modulus of soil mass, the influence of pile foundation on modulus of soil mass and basal heave is studied. The process of excavation is simulated by the FEM software ANSYS, the trends of basal heave with or without pile foundation are calculated, and the influence of pile space, pile length and the loading on pile are discussed. The results of calculation are the same to the results of simulation test and basically the same to the field measurement.