Abstract: The characteristics of Drucker-Prager yield surface transformation during the strength reduction process by strength reduction finite element method in slope stability analysis under the plane strain condition are analyzed. Currently, the Mohr-Coulomb hexagon circumcircle Drucker-Prager criterion is adopted in the ANSYS finite element analysis programme. So, the safety factor using ANSYS with the Mohr-Coulomb hexagon circumcircle Drucker-Prager criterion is calculated; thus the safety factor based on the Drucker-Prager yield criterion such as the Mohr-Coulomb matching Drucker-Prager yield criterion under the plane strain condition can be obtained using the deduced conversion formulae. Under the plane strain condition, the Mohr-Coulomb yield criterion in the ANSYS programme without secondary programming development through equivalent substitution is adopted. The safety factor conversion formula with different Drucker-Prager yield criteria is deduced. The safety factors calculated with conversion formula and those calculated by traditional method are compared through slope models analysis using ANSYS, and the error between the results obtained by strength reduction finite element method with different Drucker-Prager yield surfaces are investigated. A series of case studies indicate that the average error of safety factors between those obtained by conversion formula and those by calculation is slight. The applicability of the proposed method is clearly verified

Key words: slope stability analysis, strength reduction finite element method, Drucker-Prager yield criterion, safety factor conversion