Abstract: A random vibration analysis model of arch dam – foundation interaction, which couples the pseudo-excitation algorithm and FE-BE-IBE time domain procedure, is presented. It can conveniently include the effects of arbitrary coherency on the seismic responses of arch dams. To verify the accuracy of the proposed model, Monte Carlo method is employed to calculate the seismic responses of an arch dam. The results demonstrate that the arbitrary coherency effects have significant influences on the seismic responses of arch dams.