In this paper, the two-dimensional renormalization group model for the failure process of a locked patch is designed according to the locked patch concept and renormalization group theory. The stress transfer among the blocks is defined with the conditional probability method. The critical probability P* of locked patch is obtained. By analysis the possible linkage between the failure mechanism of locked patch and evolution of landslides, it is found that the critical instability displacement of landslides has a dependency on the displacement at the onset point of accelerating creep, the number and the homogeneity of locked patches. At displacement less than the critical displacement, virtually no locked patch fails on a large scale. Above the critical displacement, the locked patch fails. After the failure of the last patch, the landslide would occur.