Abstract: In order to investigate the axial compressive behavior of alkali activated slag concrete filed steel tube(AASCFST), five specimens of axially compressed stub columns are fabricated with different dosages of expansive agent, then axial compression test is carried out. Test results show that the ultimate bearing capacity of specimens does not exhibit a significant change trend with the increase of expansive agent content, but the ductility performance increases gradually, and the maximum limit bearing capacity of specimens is 2% expansive agent content. The theoretical analysis results show that the code CECS28:2012 can still be used as a reference in calculating the ultimate bearing capacity of AASCFST stub columns under axial compression. Micro-test results show that the micro-cracks of core concrete can be effectively reduced by adding expansive agent.