Abstract: Taking a rail-cum-road cable-stayed bridge as example, this paper firstly obtains the rational parameters of viscous dampers using nonlinear time history method, based on parameter sensitivity analysis of viscous dampers according to the seismic responses of the structure. Dynamic responses of the structure with different tower-girder connections when train braking or train running occurs are investigated. The control effect of viscous dampers installed between tower and girder on mitigating the longitudinal vibration of the girder induced by train braking or running is studied. It is shown that the viscous dampers installed between tower and girder can effectively mitigate the seismic responses of the structure, and reduce the longitudinal vibration of the girder and the dynamic responses of towers induced by train braking or running.