A　composite　box　arch　with　corrugated　steel　webs　and　concrete　flanges　is　a　new　type　of　arch　structures.　The　experiment　of　this　new　composite　box　arch　model　under　asymmetrically　in-plane　loading　is　carried　out.　A　FE　model　is　established　and　its　dual　nonlinear　behavior　in　the　whole　process　is　analyzed.　The　FE　analysis　result　achieves　good　agreement　with　that　of　the　experiment.　Research　results　show　that　the　longitudinal　strain　of　model　arch　meets　the　assumption　of　Quasi-Plane-Section　in　the　elastic　stage　and　the　effect　of　shear　deformation　should　be　taken　into　account　in　the　calculation　of　its　deformation.　Compared　with　the　conventional　reinforced　concrete　box　arch　and　the　composite　box　arch　with　plain　steel　webs　and　concrete　flanges,　the　calculation　method　for　the　ultimate　load　of　this　new　composite　box　arch　is　provided.