Abstract: In order to study the axial compressive mechanical performance of reactive powder concrete (RPC) filled steel tube,an experiment on circular RPC filled steel tube stub columns is conducted to test the deformation and the strain under the axial full section load.The test results show that the main deformation is in elastic stage when the load is up to its ultimate loading capacity and then the load declines to be 80%-90% of the ultimate load.The empirical formula of ultimate loading capacity for the RPC filled steel tube stub columns is suggested according to the formula of CECS 104: 99 with the referenced tested data.The strength of the concrete and the coefficient α used for CECS 104: 99 formula are extended in order to apply the empirical formula to the engineering design.The tested data is recalculated with the revised α.The calculated results are in good agreement with the tested data.It satisfies with the engineering requirements.