Abstract: Based on the dynamic mesh technique, the vortex-induced vibration of wind turbine airfoil at 90° angle of attack was numerically studied by using the prescribed vibration method and the free vibration method respectively. Through the prescribed vibration calculation method, the vortex-induced vibration range of Du96-W-180 wind turbine airfoil at different amplitudes was determined, and the effects of changing the incoming flow velocity and changing the structural stiffness on the vortex-induced vibration range were compared. Through the free vibration calculation method, the vortex-induced vibration range of the airfoil at different inflow speeds was obtained. The influence of different structural damping on the vibration response of the airfoil at the frequency ratio r=0.93 and r=1.11 was compared, and the development and evolution process of the vortex-induced vibration of the airfoil were analyzed. Results show that vortex-induced vibration range at different frequency ratios is basically the same while changing incoming flow velocity and changing the structural stiffness. The free vibration numerical simulation verifies the vortex-vibration range of the forced vibration. When 6% structural damping is applied at different frequency ratios, the vibration of the airfoil exhibits two forms: vortex-induced vibration and forced vibration.