Concrete　eliminates　or　delays　the　local　buckling　of　steel　hollow　sections,　and　increases　the　ductility　of　the　section　significantly.　An　efficient　ductility　of　composite　sections　is　very　important　especially　under　earthquake　loading.　One　method　was　used　to　quantify　the　ductility　coefficient　of　concrete　filled　steel　tubular　columns　with　square　sections.　The　main　objectives　of　this　paper　were　twofold:　firstly,　to　describe　the　determination　method　of　the　ductility　coefficient　of　concrete　filled　steel　tubular　columns　with　square　sections,　and　secondly,　to　analyze　the　influence　of　several　parameters,　such　as　the　slenderness　ratio,　compression　ratio,　sectional　steel　ratio,　the　concrete　strength　and　the　steel　yield　stress　on　the　ductility　coefficient.　The　results　in　this　paper　may　be　a　reference　for　practical　engineering.