Abstract: Based on water-soluble mandrel, the integrated composite wing box was fabricated via resin transfer molding (RTM). The test of natural modal of wing box was conducted. The finite element (FE) models for modal and buckling analysis of wing box were generated by using 3D shell element to investigate the stacking sequence effect on the natural modal and bucking properties. The calculations of natural modal are consistent well with the experiments, validiting the FE model proposed in the paper. The FE model was applied to simulate the natural modal and stability of wing box with four different layups. The results show that symmetrical layers of the skin have significant beneficial effects on natural frequency and buckling loads of wing box under axial compression and torsion, in contrast, have distinct adverse effects on those under the bending and combination of bending and torsion. In addition, the rigidity of web has an apparent beneficial effect on the buckling load and natural frequency of wing box, whereas the increasing of 45? plies or the decreasing of the thickness of web would reduce buckling load and natural frequency.