The closed cut-off wall is widely used in the reinforcement projects of earth-rock dams. However， there are few studies of the closed cut-off wall. Further more， there are few studies of the interaction between the cut-off wall and the earth-rock dam， which consider the coupling effect of seepage and stress. In order to discuss the numerical simulation method and the principle of the wall-dam interaction in the reinforcement project， on the basis of analyzing the actual engineering conditions， a seepage and stress coupled numerical model is established by using ABAQUS. The contact of wall-dam together with the coupling of seepage-stress are taken into account in the model. The research results show that the model is feasible to simulate the interaction between the cut-off wall and the earth-rock dam， that the stress of the closed cut-off wall which is built in the earth-rock dam is mainly caused by horizontal load， and that simply ignoring the coupling effect may lead to unsafe calculation.