In connection with slope stability of soil nailing support for foundation pit, the slip surface stress analysis method and strength reducion method were used to analyze the stability of soil nailing support for foundation pit. For the slope with soil nailing support for foundation pit, the safety factors by two finite element methods were consistent; but the shapes of critical slip surface were inconsistent in different stages. The reason was that only the strength of the soil and the cement deep mixing pile were reduced during the process in the calculation; and the strength parameters of the nail bar were regarded as constant. Considering the effect of soil nailing on soil and slope, Soil nailing technology had a more realistic theory meaning in the construction.