A global optimization method for cascade blade based on Niche GAs(Niche genetic algorithms) coupled with RANS(Reynolds-Averaged Navier-Stokes) equation has been presented.In order to meet the search theory of GAs and the aerodynamic performances of cascade blade

Bezier curve is adopted to parameterize the cascade blade profile in this method

and a fitness function pertaining to optimization is designed.The design variables are the control points' ordinates of Bezier curve representing the cascade blade profile;the object function is the maximum lift-drag ratio of the cascade;the constraint conditions take account of the leading and trailing edge metal angle

and the strength and aerodynamic performers of cascade blade;and the treatment method of the constraint conditions is the flexible penalty function.The lift-drag ratio of optimized cascade is 8.3 percent higher than that of the initial one.