Compared with the traditional streamlined box girder， the typical Π-shaped open section is prone to vortex-induced vibration （VIV） because of its high section bluff configuration. In this research， the simultaneous vibration and pressure vibration of wind tunnel tests and computational fluid dynamics （CFD） are used for studying the characteristics of the pressure distribution along the surface of the typical open section and the nonlinear phenomena such as different aerodynamic components and hysteresis characteristics. First， the initial characteristics of the local pressure in different periods in the VIV lock-on region are analyzed. Secondly， the CFD dynamic grid method is used to realize the fluid-solid coupling analysis of the section. On this basis， the different frequency components of the aerodynamic forces in the VIV process are decomposed by the Hilbert vibration decomposition （HVD） method. The research results show that the average surface pressure on the leading edge of the opening section is in the negative pressure zone， where the airflow is separated. At the extreme point of the VIV， the pulsating pressure changes most violently in the area of 0.1