An efficient computational method is presented based on the thick strip method for Large-Eddy simulation of flexible wings in stall. Fluid domain is break down into series of smaller 3D strips which one independently solved using implicit LES method. Force and moments are obtained from each strips and used to evolved the nonlinear dynamics of the structure. High deformation response of high-altitude long-endurance wing under several angle of attacks leading to the stall regions are presented to show the capability of proposed FSI method