Research conclusions:(1)The track constraint system enhances longitudinal connection between adjacent bridges，two separate vibration unit obtained by traditional model analysis get into a whole vibration unit. With the decrease in number of simply-supported girder，longitudinal natural vibration period of the continuous girder bridge decreases.(2)For the continuous girder bridge，seismic response analyzed by the rail-bridge model is greater than that of the traditional model. With the increase in the number of simply-supported girder，seismic response increases significantly. No considering longitudinal stiffness of track constraint system，seismic response of the continuous girder bridge will is apt to be unsafe.(3)With the decrease of axial stiffness of track system，calculation results by using the rail-bridge model is more and more close to that of the traditional model.(4)With the increase of axial stiffness of end spine，seismic response of the continuous girder bridge gradually reduces. But when the end spine stiffness is greater than a certain value，seismic response of continuous girder bridge is almost no change.(5)The research result may provide a basis for revision of computational models of the high-speed railway bridge under frequent earthquake.