The purpose of this work is to present an optimal design method for radar brackets to get the lightest structure with stiffness constraint. Current radar brackets usually have conservative strength and excessive weight which influences the mobility of radar greatly as they are not optimized in the conceptual design stage. In this paper the well-known ESO (Evolutionary Structural Optimization) method based on ANSYS is studied and used as the method to optimize them. To begin with the criteria of ESO method and its implementation method are studied. Then a case of optimization for a phased array radar bracket is studied and at last the optimization result is compared to the result by using WORKBENCH (a commercial CAE software) and the comparison shows that this method has its unique superiority.