Abstract: In this paper, the authors develop displacement time-history response equation based on the classical structural dynamic formula.A 3D finite element model for a cable-stayed bridge is constructed to analyze the dispalacement respone under seismic.The study shows the influence of vertical force on bridge longitudinal displacement is reduced obviously while it does not exist in vertical displacement under multi-component seismic excitation.Consequently, the influence of multi-component seismic excitation should be considered for the design of cable-stayed bridge.