A structure model of three-span continuous rigid frame bridge was constructed based on the finite element method. At first, the modal analysis was performed to get the natural frequencies and periods. The dynamic characteristics of the bridge structure were summarized, and some improvement measures are suggested to overcome the shortcoming for the bridge structure. Then, seismic response analysis was carried out based on the EL-Centro wave. The input excitations adopted the combination of vertical wave plus longitudinal wave, or vertical wave plus lateral wave. Based on the two excitation cases, some useful results were obtained, which include internal forces, displacements, accelerations time-history curves of the critical sections for the bridge structure. And some commentates about the time-history curves are given. At last, some helpful conclusions are drawn based on the calculation and analysis above. The calculation methods and results in this paper can provide some referenced information for the engineering design.