Abstract: A brief introduction to the available main methods of calculating the axial compressive strength of steel tube-reinforced concrete composite columns is presented. The ultimate state of axial compressive strength of composite columns and a formula for calculating the peak compressive strain of the composite column are proposed. Based on those, formulae for calculating the axial compressive strength of composite columns are developed. The axial compressive strength of 34 composite column specimens are calculated by the developed formulae, the calculated results have good agreement with the test results. In order to make the peak compressive strain of the composite column less than the peak compressive strain of the stirrup confined concrete out of the steel tube and larger than the peak compressive strain of the steel tube confined concrete, the upper limit value of the proportion of the steel tube confined the concrete area over the overall sectional area of the composite column is suggested.