Abstract: The landslide mode of retaining wall collapse is a kind of typical failure mode of large-scale rock slopes. The physical and mechanical properties of the locked patch play a key role in maintaining the stability of such slopes. Based on the force analysis of the slopes, the upper sliding mass can be divided into several calculation slices according to its geological structures (for example, bedding planes), and then the forces (including magnitude and direction) applied on the locked patch can be efficiently determined based on the upper bound method of limit analysis. On the basis of limit shear balance analysis, the safety factor of the locked patch with shear failure mode can be calculated. Xikou landslide in Sichuan is taken as a case study to verify the practical application of the theory proposed by the authors. Firstly, the most dangerous section in the locked patch can be obtained according to the relation between safety factor and dip angle of the shear plane. And then the relationship between the width of the most dangerous section and the safety factor is quantitatively analyzed. These results are of great significance for the stability evaluation and hazard control of the landslides with the failure mode of retaining wall collapse.