Abstract: In order to study the suppression mechanism of vortex-induced vibration （VIV） by adding aerodynamic countermeasures such as guide vanes near maintenance rails and spoilers on handrails， the displacement and pressure measurement on a large-scale sectional model was conducted in wind tunnel tests. Based on the spatial-temporal distribution and statistical characteristics of surface pressure， an aerodynamic wave hypothesis is proposed and further verified using the spectral proper orthogonal decomposition （SPOD） method. Moreover， the complex spatial-temporal pressure field is quantified and deconstructed with the spatial-temporal energy spectrum of the aerodynamic force， revealing the mechanism of vertical VIVs as well as its suppression by aerodynamic countermeasures in a streamlined box girder. The results reveal that there are three lock-in ranges of vertical VIVs for the original girder while the largest VIV response appears in the 3rd order lock-in range. The addition of guide vanes near maintenance rails reduces the maximum amplitude of model displacement by 53.1% whereas the installation of spoilers on handrails eliminates VIVs. The complicated pressure field on the girders surface can be expressed as a linear superposition of aerodynamic forces related to multiple spatial-temporal distribution modes induced by different excitation sources. The pressure on the original girder is dominated by the 1st order SPOD mode where the component at the fundamental frequency of bridge girder is the main ingredient. Meanwhile， the spatial-temporal distribution mode of aerodynamic force on the upper surface contribute more to the VIVs. The predominant aerodynamic forces mode distributing harmonic on the upper surface travels downstream， with the contribution value presenting a wave-like distribution， collectively referring to as the “aerodynamic wave effect”. The aerodynamic wave intensity acting on the upper surface is much greater than that of the lower surface. The propagation of the aerodynamic wave could be characterized by the monotonously decreasing phase lag between the distributed aerodynamic forces and the vortex-excited forces （VEFs）. The wavelength of the aerodynamic wave on the original girder is approximately consistent with the wavelength of the contribution value， which corresponds to the distance between the windward and leeward crash barriers. With the addition of guide vanes near maintenance rails， the predominant mode of aerodynamic wave on the upper surface is similar with that on the original girder while the wave intensity decreases， resulting in a reduction of VIV response. The spatial-temporal energy spectrum of aerodynamic force on the upper surface turns into a broadband distribution after the installation of spoilers on handrails， and the frequency lock-in phenomenon disappeared. Thus， VIVs were eliminated. This study provides a new perspective for the analysis of pressure field on girder surface and constructing mathematical models of the vortex-excited force on bridge girders， which could deeply reveal the mechanism of VIV.