A limit equilibrium method is proposed for analyzing progressive failure in the stability of brittle soil slopes. In the proposed method, the failure surface is firstly assumed and the whole failure mass is divided into many vertical slices. By satisfying force and moment equilibrium for each slice as well as for the total mass, the overall factor of safety for the assumed slip surface can be calculated. This factor of safety is then used to check the state of stress along the bottom of each slice. If the state of stress exceeds the soil strength, then local failure occurs and the residual strength is assigned. The whole procedure will be repeated unless the propagation of local failure zone stops. Finally, a more reasonable definition for factor of safety is determined. This analysis is illustrated for well documented case records, and the results are quite consistent with the field observations.