Π-shaped composite deck is an elastic bluff body， which is susceptible to aerodynamic instability. In the present study， a cable-stayed bridge with a Π-shaped composite deck is taken as the research object， and the vortex-induced vibration （VIV） and the aerodynamic countermeasures are investigated by using the small-scale wind tunnel tests and computational fluid dynamics （CFD） method. The wind speed range of the VIV for the Π-shaped composite deck is determined via the wind tunnel test. After that， several VIV mitigation measures are investigated. The computational fluid dynamics （CFD） method is used to study the mechanism of VIV and vibration suppression by aerodynamic measures. The results indicate that the VIV in the original section is caused by the interaction of the periodic shedding of the vortex in the wake area and the vortex evolution on the upper and lower sur? faces of the girder； After adopting three different aerodynamic measures， the flow can pass through the section more smoothly， so as to mitigate the VIV effectively， except for the upper inverted L-shaped guide plate at the wind attack angle of +3°. This study can offer guidance on the wind-resistant design of a cable-stayed bridge with a Π-shaped composite deck.