Abstract: In connection with soil nailing support for deep excavations, the calculation of safety factor by finite elements based on the concept of reduction of strength parameters is discussed, including the three dimensional finite element models for soil nailing, the colculation of safety factor through reduction of strength parameters, the identification of limit state and calculation techniques for limit state analysis. A computer program is developed based on the proposed computation model, and numerical examples are given to show the reliability and effectiveness of the model. Moreover, the comparability between the safety factor calculated by FEM and that by the formula in the current design code is also discussed.