Abstract:Xiaowan Hydropower Project is located on Lancang River of Yunnan Province in China. The dam is 292 m high,13 m wide at the top,about 69 m wide at the base and has a maximum capacity of electrical generation of 4 200 MW. The sixth slope is near the dam on the left bank. When digging a road,part of the sixth slope began to slide. For security of the project,countermeasures have to be taken. So it is necessary to find the potential instable zone,which is of the most concern. Through investigation,it is known that landslide happens along original joints and faults,and it is speculated that the next landslide will continue to happen along them. By analyzing the location of joints and faults and the deformation failure mechanism of landslide,the possible unstable zone is deduced. Based on plentiful investigation data and the test results,a numerical model of the sixth slope is built with ANSYS,and the joints and faults are modeled with low strength materials. Results show that the stress and strain of the slope change after landslide. By comparing the tracks and curves of the stress and strain before and after slides,the potential instabe zone of the slope is identified;and countermeasures are designed. The study shows that the identification of the zone by both methods is consistent and this approach is practicable and the result is believable.