Abstract: Based on plasticity limit analysis by upper bound theorem,a new method to analyze rock slope stability was put forward.It was known that the inside of rock mass would generate shear failure along some old steep discontinuities(faults,joints and bedding planes) when sliding damage took place.According to the phenomena and virtual work rate equation in limit state,a different failure mode of inclined slices technique was established,and the computing formula of safety factor was also derived using the theory of plasticity limit analysis.By means of overload factor,the safety factor of slope stability could be easily expressed by the critical loads.As a result,not only the implicit expression could be avoided,but also the safety factor could be calculated simply and effectively.As a practical engineering example,the right bank slope of Jinping First Stage Hydro power station was analyzed.It was shown that the new method was accurate and significant for rock slope with inclined interfaces.