Abstract：Based on the field investigation，the deformation mechanism of a large-scale soft foundation landslide is discussed in the area of hydroelectric power station in the upstream of Yellow River. The soft foundation slope is composed of soft rockmass in lower part and hard rockmass in upper part. It is demonstrated that the evolution of this kind of slide is always initiated by the compression of the lower soft rockmass，then the tension fracture and toppling of the upper hard rockmass occur，and at last the landslide of creep sliding-tensile fracturing type would occur along the shear stress concentration zone in the slope．
