Abstract: Nonlinear FEM strength reduction is a slop stability analysis method which is widely cared in the geotechnical field. With the anti-shear parameters c-φ reduction, the nonlinear FEM model of slope reduced to instable status and the numerical non-convergence occurred simultaneously. And then the safety factor was obtained by c-φ reduction algorithm for which can be regarded as equal to stability factor. In this paper, some reservoir slope nonlinear contact analysis was made and the calculation results showed that it accorded well to the traditional grid limit equilibrium method. Therefore, it showed that strength reduction FEM was feasible to assess slop stability.