Abstract: The effect of the variation of soil shear strength parameters with depth on slope stability considering spatial variability of soil parameters has not been studied systematically. A probabilistic method is proposed for infinite slope stability analysis considering the variation of soil shear strength parameters with depth. First, the Karhunen-Loeve expansion is adopted to simulate the random field of spatially varying soils. Second, the effect of spatial variability of soil parameters on failure probability and critical slip surfaces is investigated. Finally, an infinite slope is presented to demonstrate the validity and capacity of the proposed method. The results indicate that the spatial variability of soil shear strength parameters has a significant influence on the failure probability of the infinite soil slope. The failure probability decreases with the increasing correlation length of soil shear strength parameters. For an undrained clay slope, a significant change in the undrained shear strength parameter varying with depth results in a smaller failure probability. Most of the critical slip surfaces will occur at the base of the slope. For a frictional/cohesive slope, the failure probability does not monotonically decrease with the increase of the variation of the soil shear strength parameters with depth. The trend of shear strength varying with depth has a significant influence on the critical slip surfaces. If the trend of shear strength varying with depth is ignored, it is most likely that the critical slip surfaces will occur at the base of the slope.