The sliding process of the landslide is gradual, and it is impossible for all points on the sliding surface to be in the state of peak shear stress. Therefore, it is reasonable and necessary to consider the stability calculation of the progressive failure process of landslide. In view of the existing stability analysis methods considering progressive failure of landslides, it is unreasonable to define key blocks incorrectly and adjust sliding surface parameters at different stages to consider the stress softening phenomenon of soil mass, which causes damage to the continuity of shear stress and strain curve of soil mass. To more closely consider the progressive process of landslide failure and more accurately describe the different stress states of each point on the sliding surface, the concept of landslide key block is proposed. The concept of the key block of landslide is put forward, and the displacement of landslide is introduced into the stability analysis of landslide by a new shear stress model. Based on the unbalanced thrust method, a new displacement-resistance method (NDR) is established, and the calculation formula of landslide stability is given.