An　improvement　to　the　Direct　Stiffness　Calculation　(DSC)　method　and　corresponding　new　damage　index,　Stiffness　Variation　Index　(SVI),　is　proposed　in　this　paper.　SVI　is　a　parameter　related　to　modal　curvature　and　bending　moment　calculated,　respectively,　by　central　difference　scheme　to　displacement　and　integral　method　to　load.　The　proposed　improvement　makes　the　DSC　technique　applicable　to　damage　detection　of　practical　bending-type　structures.　Research　on　the　effect　of　measurement　errors　was　performed　through　numerical　simulation.　Moreover,　a　continuous　steel　beam　was　tested　to　verify　the　modified　DSC　technique　in　the　condition　of　concentrated　damages.　The　limitation　of　measurement　points　and　number　of　modes　are　discussed.　The　results　show　that　the　improved　direct　stiffness　method　is　feasible　and　efficient　in　the　damage　detection　of　bending-type　structures.