Inner force of soil nail is a key parameter of soil nailing design. Virtual excavation stress is used to simulate the excavation status of soil nailing. On the basis of the hypothesis that there exists no load on the face of soil nail

a calculation model is presented that the distribution of shear forces between soil and nail is double-triangle. The calculation formulas of axial force and shear force of soil nail are derived. The lateral displacement of soil at potential break surface and the end of nail by the virtual excavation of soil shear stress is obtained based on Mindlin strain solution. The zero relative displacement and the equivalent axial force of soil nail at both sides of potential break surface can provide two equations for two unknown coefficients of the calculation model. The measured data from French research test on soil nailing are used to illustrate the validity of the proposed calculation model