Abstract: To realize fatigue-resisting design for bolts and lightweight design of the flange for the large-scale horizontal axis wind turbines,the nonlinear relationship between the external load and bolt stress is established. Thus the timing stresses of the bolts can be calculated in term of the linear interpolation of the timing load. The effect of the inner diameter and thickness of the flange on the cumulative fatigue damage is investigated. Aiming to minimize the total weight of the flange,the formulation of structural optimization for the flange subject to the constraint on the fatigue damage is presented and solved. The optimized results revealed that the lightweight design of the flange can be achieved under the premise of ensuring the fatigue strength of bolts.