Abstract: FLAC-3D is used to analyze a simple slope The comparative analysis of the safety factors which were calculating by convergence criterion, plastic zone criterion, effective shear strain increment criterion and displacement mutation criterion. By the selection of the "feature points" and "mutations criterion for analysis,The top of the hill and the slope midpoint of displacement monitoring is more effective than detecting the foot of the slope at the displacement; mutations only from the displacement size as a criterion standard is not stringent enough,and propose a feature point by observing the displacement reduction factor curve slope changes determine the safety factor, the slope of the mutation at the corresponding reduction factor is the safety factor.