Abstract：The stability of Shuiwenzhan slope after impoundment is very important to each correlative department because it affects the dam safety and its usage. The results by 3D numerical modeling indicate that there are three failure planes in the slope，a major failure plane and two secondary ones. The connectivity of the major one is low and the others are high. The results also indicate that its deformation is little and it is stable in general in the primary stage；With the impounded water level rising，its deformation increases. There is a large local deformation or damage while the impounded water level reaches 1 850 m. The deformation and damage become bigger and wider leading to partial failure while the impounded water level is up to 1 880 m，but in a whole，it is still stable，and it could only slide in middle-superficial layer.
