Abstract:A dynamic interaction model of train and bridge was established considering beam rail and wheel rail relation. Based on the characteristics of high speed railway system, the rail was modeled as a discrete point support Euler beam and the motion equations of the bridge was built using a modal synthesis method. Furthermore, the effect of track irregularity, running speed and beam span on the dynamic reaction force of piers was analyzed with respect to the characteristics of simply supported box girders in China. It is concluded from the results that the track irregularity with medium and long wavelengths do not have significant effect on the dynamic reaction force of the piers. With increasing running speed, the resonance and vibration cancellation of the beam enlarges and reduces the dynamic reaction force of the piers respectively. The dynamic reaction force characteristics differ significantly under different spans, and different dynamic force frequencies caused by carbody length and wheelbase can be observed at different degrees.