Abstract: In the paper, the limit load formulae for a thick-walled tube with different strengthin tension and compression state are derived based on the twin shear unified strength theory, underthe action of an inner pressure and axial force. In these formulae, theresults with Trescacriterion, linear approximate Mises criterion and twin shear stress yield criterion can beobtained with different coefficient values reflecting the middle main stress effect, andlimit loading curves for different yielding criterions are plotted.Therefore, accurate solutions forlimit loads can be obtained with this theory under thethree-dimensional state; the limitloading diagram is consistent to yielding curves of twin shear stress, Mises and Trescacriterions; these formulae can be used for the material with differentia strength in tension andcompression state.