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