At present,most of the research on gravity dam only considers the damage of the dam body,and the dam foundation is made of linear elastic material,which may cause the dam earthquake damage to be inconsistent with the actual situation.Considering the plastic damage of the dam foundation,it can significantly reduce the damage degree of the gravity dam body,which can more realistically simulate the seismic bearing capacity of the dam.Based on the theory of plastic damage mechanics,it takes a proposed gravity dam in the southwest of China as the research object,a three-dimensional finite element dynamic calculation model considering the overall plastic damage of the dam body and the dam foundation is established,and the correctness of the model is verified.The seismic damage of the gravity dam under different earthquakes intensity is analyzed by the time history analysis method,and the ultimate seismic capacity of the dam is evaluated with the dam body cracks penetrating the upstream and downstream as the criterion of instability.The results show that when the ground vibration intensity is 0.5g,the damaged area at the downstream slope is connected to the upstream.Meanwhile,the upper dam body of the gravity dam can be regarded as a detached block,and the gravity dam is unstable.Therefore,the ultimate seismic capacity of the gravity dam can be determined as 0.5g.