Experiment　on　an　external　prestressed　reactive　powder　concrete　(RPC)　box　girder　model　subjected　to　symmetrical　concentrically　load　is　carried　out　Experimental　results　show　that　the　model　failed　due　to　the　tension　steel　bar　yielding,　and　the　RPC　in　compressive　zone　was　not　crushed.　Anti-cracking　capacity　of　RPC　box　girder　is　better　than　normal　reinforced　concrete　(RC)　girder.　Same　as　RC　girder,　the　plane-section　assumption　is　satisfied　and　can　be　used　for　sectional　analysis　in　the　test　model.　The　shear　lag　is　not　produced　at　the　elastic　stage　in　the　girder,　for　it　has　just　a　little　difference　among　the　strains　on　the　top　flange　at　the　mid-span.