Abstract: On the basis of analyzing the current design and calculation methods of soil nail, the authors point out their deficiency and put forward a new method based on limiting equilibrium. To check the reliability of this method, an in-situs test of the interior force of soil nail in a practice engineering was made. The measured results show that the actual force of the nail is only a eighth of the result from the current calculation method. But the proposed method by the authors can produce very close result to the in-situs measured ones.