A wind turbine tower optimization program was developed, using a genetic algorithm. This allowed a rational analysis to reduce the mass of turbine tower, by considering, for example, the distributions of diameter and wall thickness, and the positions of flanges and access ports to navigation lights. Both extreme and fatigue loads were calculated, based on wind turbine design requirements and the Building Standard Law of Japan. Therefore, the aero-elastic characteristics and the controller of each turbine were considered. Furthermore, sensitivities to some representative design parameters were also investigated in case studies of the SUBARU80/2.0, 2MW turbine.