Abstract: Based on the effective failure criterion and the stiffness degradation model for composite material, the ultimate strength of stiffened laminated plates is studied. The analysis model is established by nonlinear degenerated laminate three-dimension shell element method, which is derived from the incrementally updated Lagrangian formulation. In order to obtain the accurate ultimate strength of the plate, a new criterion for judging the singularity of the solution matrix is presented. The effects of stacking sequences and thickness of lamina on the compressive ultimate strength of the plate are discussed. Comparisons between analytical solutions and test results indicate that the nonlinear degenerated laminate three-dimension shell element model is an effective way to analyze the axial compressive ultimate strength of composite laminate stiffened plates. The judgment criterion proposed in this paper improves the validity of analytical results.