Abstract: The structual strength of blades is a significant factor of the safety of wind turbines and the levelised cost of energy. A three-dimentional finite element model was built to investigate the strength of blade segment, which inherited the geometrical and laminate cross-sectional characteristics of American SNL 100 m glass fiber reinforced polymer composites(GFRP) blade at critical span location. The coupling behaviors of nonlinear buckling, adhesive debonding and composite failure were jointly studied. The results indicate that composite of blade segment fails firstly, then the adhesive debonds, and the adhesive breaks finally under the flap-wise load. Nonlinear buckling initiates firstly, then the composite fails and adhesive debonds, and the adhesive breaks finally under the edge-wise load, which implies that the adhesive debonding at trailing edge is triggered by the buckling deformation.