Utilization of wind power in Indonesia is less attractive compared with utilization of conventional fuel. This is because the price of wind energy is not competitive when compared with fossil energy prices, and as a result of the implementation of energy pricing policy through subsidies. Before designing the Wind Energy Conversion System, simulation of computational fluid dynamics needs to be done in order for reducing designing time and cost. In this research, modeling and simulation work has been done to figure out the optimum aerodynamics coefficient of wind turbine blades at different Reynolds number. This blade is a modification of standard airfoil of NACA 4415. The aerodynamics coefficient of modify and standard airfoil is then compared. FLUENT software and Spalart-Allmaras Turbulent Model are used in this work. Based on the comparison of the coefficient of aerodynamic, modification NACA 4415 airfoil has better performance at Reynolds number of 4.1 × 104 to 2.5 × 105. The experiment results also showed that based on a numerical study of the modification NACA 4415 airfoil can be used as a basis for the establishment of wind turbine blades.