Abstract: A novel structure termed as concrete filled steel tube-seawater and sea sand concrete (SWSSC) filled fiber reinforced polymer (FRP) tube composite columns was proposed, which was composed of outer steel tube, sandwiched ordinary concrete, inner FRP tube and core SWSSC. The sandwiched ordinary concrete was confined by the outer steel tube, while the core SWSSC was confined by both steel tube and FRP tube under axial compression. Considering the different confinement mechanism of two kinds of concrete, the calculation models of peak point and ultimate point of concrete filled steel tube-SWSSC filled FRP tube composite columns were proposed based on the existing calculation model of concrete-filled FRP-steel composite tube columns. And the predicted stress-strain curve model was obtained by using the stress-strain curve model of concrete-filled FRP-steel compo-site tube columns. The proposed model was verified and evaluated on the basis of the existing test results. The results show that the proposed model can predict the stress-strain curve of concrete filled steel tube-SWSSC filled FRP tube composite columns well. Finally, based on the proposed stress-strain model, the axial compression behavior of concrete filled steel tube-SWSSC filled FRP tube composite columns with different parameters was analyzed.