Abstract: In view of the strength reduction method used for slope stability analysis frequently, the stability of the homogeneous slope and the slope with weak interlayer, which are reinforced by piles, is analyzed by means of the commercially available finite element analysis software. It shows that for the homogeneous slope, when the diameter of pile is regular, the safety of factor decreases while the pile spacing increases and the pile stiffness decreases. The soil pressure increases along the depth of the pile. In the same situation, the factor of safety obtained by the strength reduction method is larger than that obtained by the limit analysis. For the slope with weak interlayer, the sliding surface develops from the foot of the slope to the top while the pile spacing is small. However, the sliding surface develops along the weak interlayer basically while pile spacing is large.