This study was a basic one to explore how much the aerodynamic characteristics of wind blade improve.The extent of improvement according to the shapes of groove placed on the surface of airfoil(NACA0015) was analyzed through computational analysis. A commercial computational fluid dynamics(CFD) code, the ANSYS Fluent 13, was used in this study. In this study, regarding with the positions andshapes of groove, the end of groove was placed at a certain distance (length, l) from both the front andback of separation starting point, the depth and the width were designated as h and d respectively.Analysis was conducted at the 7° angle of attack under the following conditions; the thickness (δ) ofboundary layer to the depth (h) of groove ratio (h/δ) 0.6–1.0, the depth (h) of groove to the width (d) ofgroove ratio (h/d) 0.1–1.4, and the length (l) between the end of groove and separation point to thethickness (δ) of boundary layer ratio (l/δ) −0.5–0.5. Among these conditions, the best improvement of liftto drag ratio, standing at 15.3%, was under h/δ = 1.0, h/d = 0.12, and l/δ = –0.5 (7° AOA, Re = 360k). Inaddition, throughout the range of angle of attack, 2–14°, lift to drag ratio improved by 0.8%, 5.1%, 3.2%,and 1.8% each when Reynolds numbers were 280k, 360k, 450k, and 530k. It is also confirmed that theshape of groove contributed to recovering velocity around airfoil wall and the lift to drag ratioimprovements by groove were maintained at the given range of Reynolds number and around theangle of attack, 7°.