Abstract: The extreme load analysis research in a case of 4 MW large-scale wind turbine on extreme conditions is carried out by method of dynamic response coupling blade and tower,based on improved BEM theory in consideration of influence of tip/hub loss correction,dynamic stall,dynamic inflow and blade section torque. The results show that adoption of bypass loads or energy storage system for adjusting torque helps to decrease the extreme loads and inhibit structure displacement of wind turbine due to load disappear.