A　new　type　of　composite　structure,　the　composite　box　girder　with　corrugated　steel　webs　(CSWs)　and　trusses,　is　proposed　recently.　In　order　to　investigate　the　structural　behavior　under　positive　and　negative　bending　moments,　flexural　tests　of　the　continuous　girder　were　carried　out,　and　the　failure　modes,　deformation　patterns,　strain　distribution,　and　development　of　the　concrete　cracks　were　investigated.　Finite　element　analysis　was　conducted　to　investigate　the　effect　of　the　range　of　concrete　in　the　steel　tube　and　the　thickness　of　CSWs　on　the　flexural　behavior.　The　experimental　and　numerical　results　show　that　the　test　beam　has　a　good　ductility　and　integrity　under　flexural　load.　The　contribution　of　CSWs　to　the　flexural　bearing　capacity　is　very　small　and　can　be　neglected.　Besides,　the　plane　section　assumption　is　still　valid　when　only　top　concrete　slab　and　bottom　steel　tubes　are　concerned.　The　concrete　filled　in　bottom　steel　tubes　increases　the　stiffness　and　the　bearing　capacity　of　the　girder.　Equations　to　calculate　the　flexural　bearing　capacity　under　positive　and　negative　bending　moments　were　put　forward　and　then　verified　with　experimental　results.