Abstract: Now the analysis of slope stability generally adopts the small deformation finite element method,and the failure criterion is still controversial. Based on the coupled Eulerian-Lagrangian（CEL）approach,a large deformation finite element method,the stability of soil slope is investigated. The effects of mesh size,step time,initial geostatic stress on the calculating results are quantified. The applicability of energy aberration criterion and plastic failure zone criterion is discussed. By comparing the published numerical results,the effectiveness of the CEL model is verified. By comparing the results from different failure criterions,the energy aberration criterion is recommended for the CEL approach. For the plastic failure zone criterion,the critical cumulative plastic strain（Pc）is proposed,which quantifies the determination of stability factor. With the 113 calculated results from the parametric study,an empirical formula is established to calculate the stability factor of soil slopes,whose efficiency is also verified.