In order to establish a numerical method for the buckling, post-buckling and breaking of composite stiffened panel under compression load, the stability of compression test and the finite element method are researched for composite stiffened panel. The eigenvalue solver is used to analysis buckling of stiffened panel, and the buckling mode, the buckling eigenvalue and the buckling load are obtained. And the buckling load of arc-length method and the post-buckling behavior are obtained from the curves of load-displacement using arc-length method. The carrying capability in post-buckling process is obtained when introducing the damage criterion into the model. Contrasting the two methods and test results, some conclusions can be obtained: The carrying capability in post-buckling process is greater; the eigenvalue solver method is more accurate than the arc-length method in buckling analysis, but the arc-length method can simulate post-buckling behavior better; the results of numerical method and test fit better.