Earthquake is a kind of natural disaster which is difficult to predict and the damage degree is very great, occurrence of the strong motion often leads to the tremendous life and property loss. Bridge is an important part of the lifeline engineering, it is very necessary to conduct the comprehensive and systemic investigation on the bridge aseismic. In this paper, a 670.56m span cable-stayed bridge was chosen as object of study, the FEM model of it was established, and the dynamic characteristic and nonlinear seismic responses under uniform and traveling-wave excitations were systematic studied. The results show that: 1) the mode of connection between the pier, tower and the beam is crucial to the dynamic response of bridge which should be simulated correctly. 2) Its former 10 rank frequency are located very close which shows that more mode shape should be taken into account when dealing with the dynamic analysis. 3) The traveling-wave excitation has appreciable impact on such kind of cable-stayed bridge, especially on the more flexible component, which should be paid much attention to while design.