Abstract: In engineering practice, strains are used for stress analysis of composite aircraft structures, instead of stresses due to their stacking sequence dependence. Besides, for composite airplane, damage tolerant design is necessary, the compliance of airworthiness for composite structures with damages, especially barely visible impact damages (BVID) should be assessed. Thus for civil aircraft structural design, a credible strain based failure criterion for composites that containing damage is in demand for stress prediction. In this paper, a combined strain failure criterion for laminates was introduced. In order to verify the conservation of this failure criterion, biaxial loading tests were designed. Quasi-isotropic T800 carbon fiber reinforced epoxy resin matrix composite laminates with BVID were used for in-plane failure tests under various load conditions. Various load conditions with different combination of tension, compression and shearing loads were obtained through diversified design of load ratios. It is shown from the comparison of theoretical results and test results that all the theoretical failure loads are lower than experimental ones with a ratio of about 80%. The criterion is conserved to assure the safety of structures, but not too conserved to bring unnecessary weight to structures, thus it is suitable for engineering exercise.