Taking　the　Nanshan　Bridge　as　prototype,　the　experiment　of　twin-box　single-chamber　box　girder　with　corrugated　steel　webs　scale　model　was　performed　and　the　spatial　finite　element　model　was　established.　The　investigation　of　the　whole　process　of　the　combination　box　girder　under　loads　and　the　influence　of　the　cross-girder　on　this　combination　box　provide　a　reference　for　practical　engineering.　The　results　demonstrate　that　the　mechanical　properties　of　twin-box　single-chamber　box　girder　are　similar　to　the　single　box　single-chambers＇.　The　strain　on　the　section　corresponds　with　the　assumption　of　plane　section　in　elastic　phase.　The　arrangement　of　secondary　transverse　beam　could　improve　the　force　status　of　the　top　flange,　but　it＇s　unlikely　to　strengthen　the　globality　of　the　two　boxes.　The　form　of　major　transverse　beam　added　in　secondary　transverse　beam　is　the　reasonable　cross-section　of　this　type　composite　girder,　which　could　strengthen　the　globality　of　the　two　boxes　and　improve　the　force　status　of　the　top　and　the　bottom　plate　effectively　with　a　small　increase　of　the　dead　weight.