In order to determine cross-section size parameters of the tail panel of a certain aircraft and validate the reliability and accuracy of the p-version finite element method, the buckling behavior of stiffened composite tail panel subjected to shear loading is studied by finite element analysis and testing. Study results show that the good correlations between the numerical results and the test results are obtained, which proves that the model can be effectively used in the engineering applications related to the buckling behavior of stiffened composite panel subjected to shear loading; the typical failure mode of the specimens is debonding of the skin and stringers; when the cross-section area of the stringers/skin is approximately equal, the cross-section of the skin is the major factor effecting the buckling load, but has little influence on the buckling modes.