Abstract: Combination traditional limit equilibrium methods and modern limit equilibrium methods, the vertical slices method is used for the slope stability analysis with circle slip surface. By the generalized internal forces between the vertical slices, an improved slices method based on circle slip surface is proposed. Through establishing the mechanics calculation formula for the circle slip slope surface, the relationship between influence coefficient of generalized internal forces and safety factor is can be brought forward, using the numerical calculation and iterative process, the slope safety factor with the changed influence factor of the internal forces can be obtained under the balanced force and balanced torque respectively. It can describe the slope stability quantitatively. The result shows that the improved vertical slices method for circle slip slope reflects the interaction between circle slip surface and vertical surface. The numerical calculation is easy with a higher accuracy.