Abstract: Seismic response of the Xiluodu arch dam is analyzed by a coupling method of finite elements(FEs), boundary elements(BEs) and infinite boundary elements(IBEs) in time domain. Effects of radiation damping of infinite foundation on dam response is investigated in the analysis. The results demonstrate that significant influence of the radiation damping on the structural response is verified. In addition, influences of several factors such as reservoir elevation, stiffness of the rock foundation and different earthquake input on the radiation damping are also studied.