Abstract: In addition to the regional geological background, heavy rainfall triggering, unsaturated soil mechanical analysis and numerical simulation of stability analysis, it is necessary to find out the main reasons for the differences between the occurrence and distribution of super large and medium to small size loess landslides, from the aspects of small and medium-sized geological structure and sedimentary phase variation. Taking the Zeketai Gallenpute Landslide of 22.75 million cubic meters in May 2002 as an example, the author adopted the methods of sedimentary phase change analysis, high-density electrical exploration, interpretation of medium and small-scale geological structure and comparison of hydrogeological conditions. The mechanism of the reactivation of the large-scale old landslide is revealed as follows. It appeared before Dec. 1985, initiated in one earthquake and triggered by heavy rainfall and the change of hydrogeological conditions under the fault control of the super large landslide. It is expected that the new model of loess landslide presented in this paper can provide a basis for the analysis of the overall stability of the super large Gallente landslide at different stages, and the regulation of the provincial highway S316 passing through it and supporting by the shallow bedrock at its lower section.