Aiming at the impact of softening contact zones between the upper waste and the lower bedrock on its stability, in this paper, the finite element limit analysis method was used to establish the numerical model of dump slopes with softening contact zones. And then the stability of dump slopes under different landfill angles, dip angles of bedrock, thicknesses of softening contact zones, softening degree was analyzed. At last the feasibility of this method was verified by a concrete dump slope. The results show that the softening of contact zones and the landfill angles have a great influence on the slope stability, while the dip angles of bedrock and the thicknesses of contact zones have a relatively small influence under the same conditions. With the increase of the softening degree of the contact zones, the absolute attenuation rate of the lower and upper limit safety factors of dump slopes can reach about 50%. With the continuous soil softening of contact zones, the length of sliding surface of the dump slope passing through the softening contact zones increases gradually, and the total volume of the sliding body increases continuously. Due to the existence of softening contact zones, the lower soil mass in the dump slopes pushes the front edge of the slope foot and pulls the back slope body to slide, and finally forms the through sliding surface from softening contact zones to the top of the slope.