Abstract: The deformed rock mass at the right abutment of the Heihe Reservoir of Xian City was formed by rotation. Thus, the analysis of its stability must be performed by three dimension method. However, current calculation methods are difficult to be put into practical use due to their complicity. This paper writes a 3-D program of the rigid limited-equilibrium method by which both the stability coefficient and the pushing force of landslide can be computed. Then, it is applied to the stability analysis of deformed rock mass at the right abutment of Heihe Reservoir. The result correlates well with real case and provide evidence for the engineering prevention.