The updated Lagrangian method of large deformation for the stability analysis of slopes is introduced; and then the equation of elasto-plastic large deformation FEM for the large deformation of slopes are presented. The strength reduction coefficient before a well-defined equivalent plastic shear strain (EPSS) running through from the bottom to the top of a slope is considered as its safety factor. The safety factors of homogeneous soil slope with different gradients are calculated by elasto-plastic large strain FEM method. The results are well coincident with the results calculated by small strain FEM; The elasto-plastic large strain(EPLS) FEM analytical results show that not only the nonlinearity of soil material but also the geometric nonlinearity in the process of failure stability is considered. So

the calculation results of EPLS is more reasonable. the large deformation method is applied to analysis of BIII2 landslide in the water supply reconstruction project from Dongjiang to Shenzhen. The results show that calculation EPSS is more similar to the actual sliding area given by geotechnical survey. The large deformation method is more suitable for the calculation of soft soil(rock) slopes or the wall of foundation pits.