Abstract: The problem of stability for wing surface structure made of composite stiffened panels was studied, and stability safety margin of stiffened panels under compression and shear loads was analyzed. A method of calculating buckling and post-buckling loading capacity of composite stiffened panels was presented and used to check the structural stability under complex loading conditions. The object for check is an optimized wing made of composites which satisfies the requirement of strength, stiffness and manufacture process. The internal force distribution of the wing under various load cases was obtained by MSC.NASTRAN, and the stability loading capacity of each skin block was acquired by the method proposed in this paper. Then the buckling and post-buckling safety margin calculation principles for composite laminated plates under complex loading were given to verify whether the stiffened panels of the optimized wing meet the stability design requirements. This method can be integrated into a structure optimization platform as a constraint.