The problem of geologic hazards in Baotaping, Fengjie County is the current focus of concern and contention in academic circles. It was first put forward in this paper that there exist 5 large-scale landslides with complex structures in Baotaping. They are developed within 2 - 4 Members of the Middle Triassic Baodong Formation (T2b2 - T2b4), whose rock is readily soluble argillaceous limestone or calcareous mudstone. The landslides have 3 kinds of occurrence mechanisms, which are (1) fracturing -dissolution -development of apricot yellow argillized zones, -sliding along these zones; (2) fracturing-dissolution of argillaceous limestone (T2b3) - argillation of the top layer of calcareous mudstone (T2b2) - sliding along the top layer; (3) dissolution of silty mudstone (T2b4)- sliding. Karst dissolution is the leading process of the 3 kinds of mechanisms, and the tectonic fractures provide the pass for the karst dissolution. It is the prerequisite to form complex landslide structures. These results laid down a theoretical foundation for the solution to a great deal of problems in the Three-Gorges Reservoir region.