By　use　of　a　simplified　stress-strain　curve　of　steel　fiber　concrete　and　coefficient　of　section＇s　coordinated　strain,　formulas　for　curvity　ductility　were　derived.　According　to　the　curvity　distribution　of　the　column,　the　curvity　distribution　was　assumed　to　be　a　broken　line,　then　the　length　of　the　straight　line　and　corresponding　load　and　displacement　can　be　calculated.　The　method　of　calculating　theoretical　load-deformation　curve　was　presented.　Comparison　between　testing　results　and　calculating　results　indicated　that　the　formulas　for　ductility　coefficient　and　theoretical　load-deformation　curve　are　well　verified.