Abstract:Valley stress field is one of the most important factors affecting the stability of engineering rock mass. In the dam site of Changheba Hydropower Station on Dadu River,the valley is deeply incised;and the slope made up of granite and quartz-diorite is high and steep. The adit wall splitting and discal drilling core show it is in a high stress zone. The aperture deformation method is used to test the stress field in deep slope;and the adit wall stress restoration method which is simple,rapid and economic,is adopted to test adit wall stress field on different levels in this area. Test results indicate that in this area,the slope stress field has obvious zonation;and the curves of slope stress and depth is hump-shaped ones. From outside to inside,the slope stress field can be divided into four parts,i.e. regions with stress reducing,rising,fluctuating and stabilizing. The horizontal depth of the region with stress reducing on the right bank is less than 36–54 m,while on the left bank it is less than 65–95 m. The horizontal depth of the region with stress rising on the right bank is approximate from 40 to 90 m,while on the left bank it is from 65 to 125 m. Meanwhile,the horizontal depth of the region with stress stabilizing is greater than 360 m;the stress is more than 20 MPa,even to be 31.96 MPa;and the maximum principal stress direction is NWW–EW. In a word,it belongs to the potential strike-sliding type,inheriting the characteristic of tectonic stress field during late Himalayan movement. The reasons about zonation of slope stress field are also analyzed briefly. The results are of great significance to the study of the slope stress field of deeply incised valley.