a 2D elastoplastic FEM is used to analyze the behavior of a soil nailing support for deep foundation pit; and stability method based on slip surface FE stress is applied to evaluate the stability of the soil-nailed wall. The variations of tensile force of soil nails and deformation of foundation pit are studied. The influence of different lengths and layouts of soil nails on stability and deformation of foundation pit is also analyzed. The result indicates that the potential slip surface of foundation pit is consistent with the position of maximal tensile force when the soil nails are long enough.