CFST　Composite　Truss　Girder　Structure　is　composed　of　concrete　top　slab,　CFST　bottom　chord　and　steel　truss　web.　Taking　Sichuan　Ganhaizi　Bridge　as　an　example,　the　experimental　research　on　flexural　behavior　of　a　two-span　CFST　composite　truss　girder　was　carried　out.　Focus　on　the　analysis　of　the　deflection,　the　stress　distribution,　the　failure　mode　and　the　ultimate　capacity　of　the　segments　of　positive　and　negative　bending　moment　of　the　structure.　The　test　results　show　flexure-shear　failure　of　concrete　top　slab　in　the　negative　moment　region　causes　the　failure　of　CFST　composite　truss　girder　structure.　The　value　of　cracking　load　is　75KN　and　it　is　equivalent　to　2.98　times　grade　one　load　of　highway　acted　on　the　exiting　bridge.　Filled　concrete　in　the　chord　tubes　can　increase　the　member＇s　radial　rigidity,　and　axial　force　of　steel　truss　web　is　small.　This　new　composite　structure　has　high　stiffness,　good　ductility.　Under　the　ultimate　load　its　deflection　is　only　one-one　hundred　thirteenth　of　the　span.　And　the　ratio　of　the　ultimate　load　to　yielding　load　is　1.69.