Seismic design of long-span single pylon cable-stayed bridge at high intensity seismic region has been a difficult issue for designers. There is few references in this aspect at present. Based on the research achievements and the engineering background of a single pylon cable-stayed bridge at high intensity seismic region of East China, a full bridge model is established to analyze dynamic characteristics and seismic responses of the structure. According to the characteristics of excessive displacements of the pylons and main beams and greater plastic deformations of the pylons and the piers when the bridge is under strong earthquake, the damping effect of viscous dampers on the bridge is discussed. The results show that it is necessary to take measures to absorb seismic shocks. The results of this study can be as a reference for seismic design of similar bridges.