To study the mechanical properties of improved composite L-shaped concrete-filled steel tubular columns, 18 axial compression tests of improved composite L-shaped concrete-filled steel tubular columns are carried out. The influences of all parameters included steel tube thickness, concrete strength and slenderness ratio on the mechanical properties of the specimens are analyzed, and the expression of bearing capacity is proposed. The test results indicate that the waist drum failure mode, local buckling (or cracking) failure mode and flexural failure mode are occurred in tests; the steel tube thickness, concrete strength and slenderness ratio are the key factors influencing the bearing capacity, but the increase of steel tube thickness is more beneficial to the improvement of the bearing capacity, if the steel ratio is larger, the confined effect of steel tube to core concrete is stronger. The bearing capacity calculation results are in good agreement with the experimental results.