Abstract: Airfoil aerodynamic performance is greatly influenced by flow separation and turbulent flow reattachment. The effects of riblet structure on airfoil boundary layer separation and wake velocities are studied to improve the aerodynamic performance. The effects of riblet structure on boundary layer velocity distributions of the NACA0018 airfoil and the wake velocity distributions are analyzed by numberical simulations, and a riblet structure is respectively at favorable pressure gradients region and adverse pressure gradients region, which in the anterior segment and posterior segment of the airfoil. The results showed that riblet structure can effectively reduce the airfoil boundary layer separation area and the wake velocity deficit at α=6°. Especially, when the riblet structure is located at posterior segment of the airfoil, the separation of boundary layer is located and the separation ends early. The reasonable layout of riblet structure on airfoil provides a new way for flow control.