Abstract: Vortex-induced vibration is an aerodynamic phenomenon that occurs in long-span bridges at low wind speeds,and it is an issue in the wind-resistant design of long-span bridges.In order to suppress vortex- induced vibration of long-span bridges,the effects of TMD on the vortex-induced vibration of long-span bridges were investigated.The motion equations of the vibration system consisting of a bridge and TMD are established; then these motion equations are solved in a complex frequency domain,the frequency response functions of the vibration system are obtained,and the method to design optimal TMD parameters is given.The method presented is verified using a long-span suspension bridge.First,the wind tunnel test was performed using a 1:20 scale section model of the bridge in order to identify aerodynamic parameters of a linear empirical model for vertical vortex-induced vibration,then the influences of TMD parameters on vortex-induced vibration of the bridge were investigated.The TMD parameters optimization results show that the more the mass ratio,the higher the control rate,but at the same time,engineering economic and so on should be considered to determinate TMD mass; when TMD mass ratio is a constant,the frequency rate between TMD and bridges is closer to 1,and the phase difference is closer to π/2,the control rate is higher.The vortex vibration control rate will be affected when the TMD displacement was limited by the height of bridges,TMD displacement limit must be considered in the design of TMD.When the mass ratio is 1%,and optimal TMD parameters were designed,the vortex vibration of the bridge in a lock wind speed range has been effectively suppressed.