Abstract: Delamination damage was prefabricated on composite thin-wall stiffened panels used in advanced aircraft by impact test, and then the buckling, post-buckling carrying capacity and failure modes of the samples with and without damage at shear load were studied by shear tests. The result show that the delamination damage could reduce the stiffness of the composite thin-wall stiffned panel and change its failure mode, and cause the obvious local buckling appearing during shear process, and thus greatly reduced bucking, post-bucking and damage loads.