Abstract: Based on the theory of elasto-plastic finite element and reliability analysis,the slope reliability index was studied by using partial differential technique and the incremental initial stress method.During the FEM analysis,the soil mass was assumed to be realistic elasto-plastic and Mohr-Coulomb yield criterion was adopted.Two methods of elasto-plastic FEM analysis were studied and compared—one was based on the technique of Strength Reduction Method(SRM) and the other was based on the technique of Sliding surface Stress Analysis(SSA).It was concluded that the former was simple in programming and could make use of some software.Although it could get the reliability index of the whole slope,it could not calculate the location of the corresponding sliding surface,which was very important in slope stability analysis.The later,however,could give the reliability index and the corresponding sliding surface,and it ran faster than the former,but it was very complicated in coding.In the analysis of the later case,four methods of calculating the reliability index of the sliding surface and the influences of the limit state function to the reliability index and the location of the sliding surface were discussed.It was concluded that method No.3,which could consider the direction of the sliding surface,was the same as the method based on SRM substantially and was the best one among the four methods.