Based　on　the　experimental　study　of　22　reactive　powder　concrete　(RFC)　filled　circular　steel　tube　columns　subjected　to　axial　compression,　this　paper　analyses　the　load　versus　displacement　curves,　the　failure　patterns　and　the　all　course　of　work.　The　results　show　that　the　elastic　region　of　the　load　versus　strain　curves　is　about　90%-95%　of　the　whole,　specimen　with　low　confinement　factor　(ξ)　exhibits　a　rapid　softening　process　in　the　post-peak　region,　and　a　brittle　shear　failure,　while　specimen　with　high　confinement　factor　exhibits　a　gradual　softening　process　in　the　post-peak　region,　and　causes　serious　bulge　in　all　sections　and　significant　buckling　on　the　top　and　bottom　of　the　specimen.　Based　on　analyzing　the　test　results　of　40　specimens　at　home,　this　paper　also　presents　the　calculation　formula　of　the　theory-character　parameters　(peak　stress,　peak　strain　and　plateau　stress)　for　RPC　filled　circular　steel　tube　and　the　equation　for　complete　stress-strain　curve.　Calculation　methods　of　concrete　filled　circular　steel　tube　in　different　codes　are　checked　and　contrasted,　finally　the　calculation　formula　for　ultimate　loading　capacity　of　RPC　filled　circular　steel　tube　columns　under　axial　compression　is　proposed.