Abstract: The Gaolan Mountain landslide is the largest group of old landslides in Lanzhou, and the landslide front is one of the most densely populated areas in Lanzhou. In recent years, affected by extreme precipitation and green irrigation, local deformation signs have appeared in landslides, with No. Ⅲ-2 deformation being the most significant, posing a direct threat to the safety of residents' lives and property under the slope. Based on on-site monitoring data, this paper analyzes the deformation characteristics of landslides. Based on the extreme working conditions that the landslide may encounter in the future, the overall instability conditions of the landslide are determined based on quantitative methods. The results show that the surface cracking is only the extension of the local tribal water hole, and the fracture deformation is not closely related to the change of water content in the slip body after rainfall infiltration, and the overall stability is currently stable, and the daily rainfall of 36 mm has no effect on the landslide deformation. Based on quantitative calculations, the large-scale resurrection of Gaolan Mountain Ⅲ-2 is less likely. After a once-in-a-century rainfall, the stability of landslides decreases, but it will not be unstable overall; After a very low probability of heavy rainfall, the landslide may be revived; After the impact of a magnitude Ⅷ earthquake, landslides may be revived. The research results can provide a basis for local disaster prevention and mitigation and land space use control.