The structural damping and stiffness of the super-long-span steel box girder suspension bridge are small, and its vertical modal frequency is low and dense. With the change of wind speed, the stiffening girder may occur many times of vortex-induced vibration. Firstly, finite element modeling and dynamic analysis were carried out for a super-long-span suspension bridge. In order to study the multi-modal vortex-induced vibration response mechanism and effective vibration suppression measures of suspension bridge, while neglecting the effects of aerodynamic stiffness and aerodynamic damping, the simple harmonic vortex excitation mathematical model was obtained by simplifying the Scanlan empirical nonlinear vortex excitation mathematical model. Then, with the maximum displacement response of each vertical mode as the optimization objective, based on the parameter sensitivity analysis of the liquid viscous damper and the TMD parameter optimization design method, the damper parameters and TMD parameters were determined respectively. Finally, the feasibility of viscous damper energy dissipation system to control multi-order vertical modal vortex vibration of suspension bridge was discussed, and the effect of TMD system to control vortex-induced vibration was analyzed in detail. The results show that, Setting up viscous dampers between the towers and girders has an unsatisfactory effect on the vortex displacement control of the main vibration region of each vertical mode. The TMD system can effectively restrain the multi-order vertical modal vortex vibration response of the stiffening girder in the range of frequently encountered wind speed , strictly control the maximum amplitude within the allowable value, and improve the ability of the stiffening girder to resist vortex vibration deformation.