Abstract: In view of the flat steel box girder which is a commonly used form of main girder cross section,in order to investigate its vortex-induced vibration(VIV)performance,and propose effective mitigation measures,a long span suspension bridge with steel box girder was taken as an engineering example.The section model,whose scale ratio is 1/50,was employed in XNJD-1 (was employed in uniform stream wind tunnel tests).The effects of wind attack angle,damping ratio and guide vane on VIV response were investigated in detail.However,the effects of pave-ment railings and maintenance tracks on VIV response were just briely discussed as on auxiliary research object of this paper,because pavement railings and maintenance tracks are requisite at-tachments to the bridge section in the completion state and large amounts of research results have already shown that the influence of their geometrical modifications and locations on VIV response of the main girder cross section can′t be obviously mitigated.Finally,the effective aerodynamic optimization measures were presented to reduce the VIV response in a series of studies,providing valuable reference for VIV response suppression study for similar bridge section in the future. The research results show that the locked velocities and amplitudes of VIV change with the wind attack angle,and increasing damping ratio can obviously reduce the torsional amplitude of VIV, and less obviously reduce the vertical amplitude of VIV.Removing the pavement railings or maintenance tracks can obviously reduce the amplitudes of VIV and improve the velocities of the first vertical vibration and the torsional vibration,and sometimes even eliminate the VIV response.Above all,the VIV response of this bridge section,whose wind fairing is short and blunt, can be effectively suppressed by installing the wide guide vane at the wind fairing,but the suppres-sion would be ineffective if the wide guide vane is installed at the beam bottom.Furthermore,the structure of this measure is relatively simple so it can be convenient for engineering purpose.