A powerful intensifier of friction in air flows affects the lift and drag coefficients, the flow separation plays a vital part in aerodynamic characteristics for technical applications. The porous air blowing is also one of a powerful technique that determines and improves of these characteristics. In present work the influence of this technique on power coefficient in separated laminar flow over wind turbine blade is investigated in numerical and optimization methods. The influence of some parameters associated with using air blowing, such as the speed air blowing ratio (U_j/U) strength on the performance of the NACA 4415 two dimensional airfoil at different angle of attack(5^o، 〖10〗^o، 〖15〗^o) have been studied. The result shows that the air blowing is effective in controlling the separation in all cases but the power coefficient is greater in α=5 than the other angles and at tip speed ratio equal 2.5. The influence of air blowing technique on the power coefficient is clear and greater than without blowing cases.