Abstract: In order to investigate the vortex-induced vibration performance of long-span suspension bridges and propose effective mitigation measures, a long-span suspension bridge with steel-box girder was taken as an engineering example. By a section model wind tunnel test with a scale of 1∶20, the effects of railings, maintenance rail and guide vane on the vortex-induced vibration performance of main girder at a low damping were investigated, and the mitigation measure of setting guide vane inside the maintenance rail was applied in bridge engineering. In addition, the mechanism of the vortex-induced vibration was discussed based on the test phenomenon. The research results show that the vortex-induced vibration can be effectively mitigated by the above measure, and the mitigation measure makes the aerodynamic shape of the main girder be more reasonable. Furthermore, the structure for this measure is relatively simple to be convenient for engineering application.