Abstract: There are three dam sites for Shaqian Power at the upriver, middle-river and downriver. Two big fissures were found along the left slope at the downriver dam, where an ancient landslide was confirmed. The stability of the landslide is important to select the place as dam site, and it also should be evaluated for the construction of the power. The boundary and geological characteristic were obtained according to field surveys. And the origin and deformation mechanism of the landslide were analyzed. Then the engineering geological model was build and the numeric modelling was carried out. The result gave the assessment of the stability of the landslide, which provided some reliable geological data for the chose of the dam site.