Abstract: The strength reduction method is employed to study the stability of two geogrid reinforced soil slopes. The heights of the slopes are 60 m and 40 m, respectively. Safety factors are calculated according to the criteria of run-through of plastic zone, displacement mutation of feature point, convergence of iteration and allowable tensile strength, respectively. The results show that different safety factors may be achieved in the light of different criteria for failure. Larger safety factor may be obtained if the strength of the reinforcement is high enough and the slope instability is merely induced by the reduction of soil strength. The slope may fail at lower reduction factor owing to the insufficient strength of reinforcement. The tensile stress in each layer of reinforcement can be obtained by means of the finite element method and be used to assign the reinforcement strength required, while the limit equilibrium method is not available in this case.