Abstarct: The geometric shape and aerodynamic performance of fins of wind turbines play an important role in their power factor. Traditionally, reduction of the drag coefficient and increasing the lift coefficient is applied in order to reduce the forces acting on the blades and increase the production capacity of the wind turbine. In this study, an improved idea in the air industry is used. A series of longitudinal slots is created along the fin, a suction according to the impacted wind speed to the wind turbines is applied inside the body of the wind turbine's fin. As the result, flow separation is delayed and the turbine's production capacity is increased. The exact geometry of the turbine blades has been extracted using a three-dimensional scan method, and the geometric defects of the turbine's geometry have been resolved by Catia, Solidworks, and Gambit softwares. The Ansys Fluent software has been used for grid generation and simulation. According to the Reynolds range, the dimensions of the wind turbine blades and the numerical solution of the steady flow around the wind turbine blades, the K-ω SST model is used. The simulation results shows that, due to the comparison of power generation at different wind speeds and variable pitch's angles of the wind turbine blade, the pitch's angle of 8 degree and wind speed of 16 m/s has the highest production power. The results illustrate that in the case of fins with longitudinal slots, the wind turbine' power output has increased by an average of 15%.