Abstract: This paper presents a finite element method to estimate local buckling stress of stiffened panels in axial compression. Proceeding from the symmetry analysis for the mode of buckling deformation, a so-called "local unit" computation model is proposed. It is also shown that for the structures with unsymmetric mode of buckling deformation the "typical unit' model leads to unreasonable results, because such a model represents a false structure far from the real one. Therefore, the universal adaptability of the local unit to instability analysis is confirmed and reasonableness of calculated results is ensured by avoiding the traditional approach which treats the unsymmetric mode of buckling deformation as symmetric one.Considering the difference of joints for stiffened panels, the assumption of simplification for attachments of sheet to riveted stiffeners is discussed. Then the original computation model has been improved to approach actual conditions. In addition, two principles for simplifying the computation model are defined as following:1.By taking advantage of symmetry of the deformation mode the constraint effect of the adjacent strip element to the analyzed object can be replaced by the condition of zero angular displacement.2.The evaluation for whole panel can be replaced by the evaluation for one local unit, because the constraint effect of the adjacent strip element to the local unit is very small.On the basis of these principles the computation model is further simplified, therefore the computer storage and the operation time are saved.Finally the moment distribution method is analyzed, and it is shown that the results obtained by presented method are more reasonable.