The π-shaped section is widely used in bridge construction because of its simple structure and good mechanical performance， but it is easy to generate vortex-induced vibration（VIV） because of its poor wind resistance. Therefore， in this paper， a bridge with π-shaped section with a side box type is taken as the research object， and the same step vibration and pressure measurement test is carried out by using a π-shaped section rigid section model with an aspect ratio of 10∶1. Moreover， the vorticity vibration performance of π-shaped section and the vibration suppression mechanism of the deflator are studied by comparing and verifying the method of computational fluid dynamics. The experimental results show that significant VIV occurs at wind attack angles of 0° and ±3°. The vertical bending and torsional VIV can be suppressed by adding a guide plate with specific form and size parameters on both sides of the section. Among them， the inverted L-shaped baffle has a significant aerodynamic optimization effect， which can effectively eliminate the VIV amplitude， while the horizontal baffle has a limited vibration suppression effect. Compared with the vertical curved VIV， the torsional VIV is more sensitive to the size of the horizontal baffle. By comparing the numerical simulation results with the surface aerodynamic pressure distribution， the inverted L-shaped baffle can optimize the aerodynamic profile of the section， weaken the scale and energy of vortex loss on the upper and lower surfaces of the section， and reduce the periodic aerodynamic force on the section， thus effectively suppressing the VIV of the section.