The embedded penstock of roller compacted concrete gravity dam in a type (1) large water conservancy project in southwest China is selected as the research object.Based on the conventional static analysis,the dynamic response of the embedded penstock in the dam under the earthquake of site spectrum design is analyzed by the mode decomposition response spectrum method.The calculation results show that the displacement and stress of the diversion steel pipe are small under the action of conventional static force,and the pressure diversion steel pipe can ensure good working performance.However,under the action of earthquake,there are obvious stress concentration phenomena at the inlet of the dam,the top of the valve chamber,the turning of the pressure diversion steel pipe and the joint of the bifurcated pipe.When the most unfavorable static and dynamic loads are superimposed,the concrete materials near these areas will exceed their tensile strength in a small range.It is necessary to carry out targeted strengthening measures in these areas to ensure the safe operation of the project.