In order to find out the influence of the attached components on the vortex induced vibration and aerodynamic characteristics of flat streamlined box girder， the main girder of a quasi streamlined bridge is selected as the research object. By increasing or decreasing the attached components of the model to simulate the bare beam and non bare beam sections， the wind tunnel pressure and vibration tests are carried out under different wind attack angles. The results show that the vortex induced vibration characteristics of the flat streamlined box girder are greatly affected by the auxiliary components of the model， and the railing section is more prone to vortex induced vibration at the positive angle of attack. At the same angle of attack and wind speed， there is a more obvious predominant frequency of the railing section， which indicates that the attached components of the model will have a greater impact on the vortex shedding of the flat streamlined box girder. The average wind pressure coefficient of flat streamlined box girder is greatly affected by the model section， but the fluctuating wind pressure coefficient is affected by the model section and wind attack angle. Different model sections will affect the average three component force coefficient of flat streamlined box girder， but its variation trend is mainly related to the wind attack angle.