To　study　the　axial　compressive　behavior　and　the　confinement　mechanism　of　high-strength　concrete-filled　circular　steel　tube　with　multiple　confinement　effects,　five　large　size　samples　with　horizontal　stiffeners,　longitudinal　stiffeners,　multilayer　reinforcement　cages,　inner　steel　tube　and　separation　steel　plates　were　designed.　The　influences　of　these　structures　on　the　bearing　capacity,　ductility,　stiffness,　and　residual　deformation　were　then　analyzed.　Combining　the　strain　analyses　and　finite　element　model　analysis,　the　confinement　mechanism　of　different　structures　and　the　coupling　mechanism　of　different　confinement　effects　were　investigated.　The　results　showed　that　the　confinement　effect　of　the　horizontal　stiffeners　was　similar　to　that　of　the　stirrups.　The　longitudinal　stiffeners　did　not　provide　a　significant　confinement　effect　on　the　concrete.　The　multilayer　reinforcement　cages　had　an　effective　confinement　effect　on　the　concrete,　where　the　confinement　effect　increased　from　the　outside　to　the　inside,　while　the　reinforcement　cages　had　a　slight　influence　on　the　concrete　outside　the　reinforcement　cages.　The　inner　steel　tube　had　an　effective　confinement　effect　on　the　core　concrete　and　had　a　slight　influence　on　the　concrete　outside　the　inner　steel　tube.　The　multicell　steel　tube　showed　the　best　confinement　effect　compared　to　the　other　structures　and　showed　the　best　axial　compressive　behavior.　In　the　confinement　mechanism　analyses,　the　calculation　method　of　the　stress–strain　relationship　of　concrete　with　multiple　confinement　effects　was　proposed.　The　calculated　F-Δ　curves　showed　a　good　agreement　with　the　test　results.　©　2023　Elsevier　Ltd