The optimization design method based on Bezier curve and bend function was presented to improve the operating efficiency of wind turbine blade. The control points of Bezier fitting curve of the airfoil bend function were taken as optimization variables, and the genetic algorithm was used to solve the optimization problem of the airfoil. The NACA3320 airfoil taken as the initial one was optimized to obtain a new airfoil. The aerodynamic characteristics of NACA3320 airfoil and the optimized airfoil were compared through Xfoil program. The results indicate that the aerodynamic performance of the optimized airfoil is significantly improved compared with that of the initial airfoil when the attack angle is in the range of 5°~10°. Especially under the condition of 6° attack angle, the lift coefficient of the optimized airfoil is increased by 63.9%, and the lift-to-drag ratio is increased by 29.8%. This design method can reduce the optimization design variables and increase the speed of airfoil optimization design.