For round-ended piers of high-speed railway bridges, two kinds of finite element model were set up to calculate the elastic-plastic seismic responses of piers: one was beam element model of the whole bridge which includes the piers and could take into account the influence of vehicle load，and the other was solid model of the piers which could explain the seismic responses of piers. According to the two models and the bending moment-curvature relationship program, the elastic-plastic seismic responses of piers were computed at different earthquake load combination, pier height and vehicle speed. The calculation results have shown that the seismic responses of piers will increase with increment seismic intensity, the influence of vehicle speed and pier height on the responses of the piers is not in a linearly increasing manner, the frequency characteristics of earthquake wave have great influence on the seismic responses of the piers, the piers step into the state of elastic-plasticity and the plastic hinge will be developed at the bottom of piers under rare earthquake. The simplified calculation formula of plastic hinge region length suited to high-speed railway bridge round-ended piers where stirrups are encrypted was presented.