The rigid body limit equilibrium method （LEM） and the nonlinear finite element method （NFEM） are often used in the analysis of anti-sliding stability of gravity dam. But LEM cannot reflect the process of progressive instability and mechanical mecha- nism on failure for rock mass while NFEM is difficult to use to solve the displacement discontinuity of weak structural plane. Combining the research with Xiangjiaba Hydropower Station project, the analysis of anti-sliding stability for segment 12# of the dam has been carried out using interface stress element method （ISEM）. The results can reflect the most dangerous location, the scope and distribution of failure zone in weak structural plane, and present the process of progressive failure in dam foun- dation as well as the safety coefficient of possible sliding body. These achievements provide an important technical reference for dam foundation treatment measures. The computational results show that ISEM can naturally describe discontinuous de- formation of rock mass such as dislocation, openness and sliding. Besides, this method is characterized by good adaptability, convenient calculation and high compatibility, thus it is regarded as an effective way to make an analysis of anti-sliding stabil- ity of gravity dam
