Abstract: In order to evaluate high rock slope stability of Tianwan Nuclear Power Plant (NPP), by using the finite differential strength reduction method, in this paper the authors have calculated and analyzed the stability of the artificial slope stability of the 3rd and 4th phase of this project. Compared to the results with that of the traditional limit equilibrium method, it can be found that the finite differential strength reduction method can simulate the slope′s stability better, also because that the constitutive relations of geotechnical materials is considered, as a result, thus stability coefficients obtained are more reasonable.