Abstract: On October 3, 2021, a large landslide occurred at the loess-mudstone interface in Nandianzi, Lingtai, its successful early warning measures preventing casualties. In order to investigate the occurrence mechanism behind the Nandianzi landslide, a basic investigation was conducted, covering the topography, lithology, hydrogeological conditions, and human engineering activities related to the landslide. Based on the characteristics and differences of the crack development of the landslide, the landslide mass was divided into five blocks. The characteristics of each block were thoroughly analyzed through qualitative and quantitative analysis. The specific sliding situation of different parts of the landslide was analyzed, and further evidence was provided for the objective rationality of landslide classification and zoning, as well as the analysis of landslide mechanisms. Ultimately, it is concluded that the main causes of landslide disasters are as follows: (1) Large-scale excavation and earthwork activities at the lower and middle parts of the slope and the toe, leading to slope steepening and reduced resistance to sliding; (2) Formation of slope depressions, causing inadequate drainage and softening of the rock layer contact surface, thereby diminishing slope stability; and (3) Prolonged heavy rainfall that leads to instability and causes significant loss. While the Nandianzi landslide in Lintai county represents a successfully averted disaster, it serves as a noteworthy case study and a cautionary example for scientifically and standardizedly approaching urban construction and rural revitalization in China. This study holds significance value for monitoring, early warning,risk assessmen, and engineering treatment in comparable regions.