The authors have investigated the engineering geological conditions of the large Hejia landslide destructed by sliding-bending mode in the Miaojiaba hydropower plant reservoir area, then analyzed the formation mechanism of the sliding-bending distortion and destruction mode of the consequent bedded slope in the thick and rigid rock mass from the landform and geostatic stress along with lithological compages and so on, at one time making use of theoretical calculation and numerical simulation. The conclusion is that the causation of distortion and destruction of the sliding-bending mode gestated and occurred in alternatively distributed soft and hard rocks is the tall and steep terrain along with the geostatic stress, the major principal stress parallel to slope-strike and the thick and pliable rock mass inside the slope.