Abstract: The buckling and postbuckling behavior of advanced grid stiffened st ructures with damage af ter impactwas investigated by numerical analysis. Based on the Mindlin first order shear effect theory and the Von Karmannon2linearity assumption , a finite element method was developed for the postbuckling behavior of the advanced gridstiffened st ructure (AGS) , considering the stiffness degradation induced by the progressive failure including fibref racture and mat rix crack. The overlap of the upper and the lower sub2laminates is overcome by a nonlinear contactelement . An effective numerical method for the postbuckling behavior of the damaged advanced grid stiffened st ructure is provided , and the conclusions obtained in this paper can be useful for the load capacity prediction of suchst ructures. The numerical result s show that the AGS st ructure still has a large load capacity af ter the local bucklingof the delaminated skin. The progressive failure analysis must be considered during the course of postbuckling analysis. Using the nonlinear contact element can avoid the overlap and penet ration phenomenon between the upper andlower sub-laminates at the delaminated region.