Abstarct: One of the most important renewable energy resources in the world is wind energy. In recent years, many studies focus on the power production from the wind, especially using wind turbines. Therefore, numerous activities (which are categorized into two general techniques i.e. passive and active flow control methods) have been organized to improve the performance of the wind turbines. Many of these activities are baxsed on the strategy of increasing the lift to drag ratio and delaying the stall phenomenon in rotor blades without consuming external energy (which is called a passive flow control method). In this thesis, the effect of the dimpled surface blade on the performance of the V47-660 kW horizontal axis wind turbine is numerically investigated. For this purpose, the suction side of the wind turbine blades is passively modified using some spherical dimples. The governing continuity and momentum equations are solved using an incompressible Reynolds-averaged Navier-Stokes solver and the k-ω Shear-Stress Transport turbulent model. The effect of dimple radius, location, and quantity on the aerodynamic performance of the wind turbine including torque and power generation, flow separation, and thrust load is studied to find an appropriate case. Then the effect of blade pitch angle and wind speed is also examined on the best-dimpled blades. The results show that dimples could be effective in increasing the torque and power generation if they are designed appropriately (including radius, location and quantity). Obtained results reveal that for the best situation, dimples could improve the generating torque by around 16.08%.