Taking　the　Nanshan　Bridge　as　prototype,　experiment　flexural　behavior　research　and　finite　element　analysis　on　composite　box-girder　with　steel　truss　webs　has　been　carried　out.　The　force　process,　failure　model　and　ultimate　carrying　capacity　of　the　new　composite　structure　has　been　analyzed,　and　it　shows　that　the　machine　behavior　is　similar　to　concrete　box　girders＇,　undergoing　elasticity　stage,　crack　development　stage,　reinforcement　yielding　stage　and　structural　failure　stage.　Analysis　on　different　sectional　box　girder　has　been　done;　the　result　showed　that　the　ultimate　bearing　capacity　for　the　prestressed　concrete　girder,　composite　box-girder　with　corrugated　steel　webs　and　composite　box-girder　with　steel　truss　webs　are　close　to　each　other.　The　rigidity　of　composite　box-girder　with　steel　truss　webs　is　the　lowest,　extra　deformation　due　to　the　axial　flexible　of　steel　truss　webs　cannot　be　ignored　in　the　calculation　of　deflection.