The differencial equation as a variation of the axis stress of the soil nail was derived by the blance condition,according to the bearing characteristics of soil nailing,the interaction between nail and soil,and the mechanical model of the transmission of the soil nail internal stress with the shear-log theory.Then the transmission equation was solved due to the boundary condition and the discipline of the internal stress transmission was analyzed.When compared with the field tested result of the soil nailing project by writing the MATLAB programs,the anastomoses between the theory analysis and the field test was good and the feasibility of the model and analysis method are proved.The result contributed a instruction significance to the design and the analysis of internal stress of soil nail structure.