Abstract：Jinping hydropower station is located at the middle stream of Yalongjiang River and the west side of Jinpingdahewan on the boundary of the Yanyuan County and the Muli Zang autonomous county of Sichuan Province. The deep fractures are well developed at the left abutment slope. By comparing engineering geology conditions of four slopes near the dam area，it is concluded that the regional crustal movement and magnitude of the tectonic stress are the essential causes and prerequisite for deep fractures. The slope structure and rock property provide material foundation for deep fractures. From viewpoint of mechanics，the mechanism of the deep fractures is similar to the deformation mechanism of left slope of Santan，which belongs to typical toppling deformation.
