Abstract:　To investigate the characteristic of coupled vibration of high speed train and bridge under seismic excitation, the effect of the railway track irregularity, different seismic excitation were compared and investigated by analyzing the coupled vibration of the JR300 high speed train-bridge system under seismic excitation. The results show that the vertical acceleration of train will be increased and approach the limit value ,but the vertical response of the bridge will not be affected obviously ,when the railway track irregularity is considered. The level of influence of the different seismic excitations is much different.