Abstract: With a volume of approximate 24×10~6m~3, Qianjiangping landslide, located in the Three Gorges Reservoir area, occurred on July 13, 2003. The landslide resulted in 14 people died, 10 people missing and 1200 people affected. After reservoir impoundment, the landslide was the first large rock landslide in the Three Gorges Reservoir area and brought great attention in society. In academia, problems of landslide type, genesis and evolution, etc. became the focus. With these questions, there are at least three opinions. In this paper, macrostructure of sliding zone was analyzed. According to stress history analysis and U-series dating of interbedded shear zone, formation process and mechanism of sliding zone was got. Main conclusions were as following: (i) Qianjiangping landslide was a new rockslide in interbedded shear zone; (ii) interbedded shear action induced large shear deformation of interbedded shear zone in early Epipleistocene; (iii) coupling of earth’s endogenic and exogenic geologic processes is the main geological history origin. Finally, some suggestions were advanced: during the prevention of landslide, it should pay more attention to new landslides and interbedded shear zones.