Through model test, the displacement of the top of the wall and the strain of the core pile with excavating were measured and the deformation and damage characteristics of the soft soil foundation pit supported by SMW was revealed. By parameter sensitivity analysis and back analysis, ABAQUS was applied to build the numerical simulation model of SMW in soft soil and the model parameters were obtained and the model was optimized. The impact of the embedded depth on the displacement of the top of the wall ,strain of the core pile, the bending moment of the core pile and the surface subside were systematic studied. The curve fitting equations of the above mentioned action effect variables with embedded ratio were obtained. Studies have shown that embedded depth was significantly influenced the working properties of SMW. When the embedded ratio reaches a critical value, the nonlinear variation characteristics of the above mentioned action effect variables will occur and the signs of foundation pit's failure will occur.