Based on unified strength theory and some essential suppositions,the ultimate bearing capacity formula of concentrically compressed stub columns reinforced by concrete filled circular CFRP-steel tube is deduced,considering the restriction of CFRP-steel tube to inner concrete and vertical bearing capacity of outer reinforced concrete.The results of the proposed formula are found in good agreement with experiment results.In the last,the effects of the total confinement factor,confinement factor of steel tube and confinement factor of CFRP on the ultimate bearing capacity are analyzed.