It　was　found　that　bypass　graft　alone　could　achieve　great　effects　in　treating　aortic　dissection.　In　order　to　investigate　the　mechanical　mechanism　and　the　haemodynamic　validity　of　the　bypassing　treatment　for　DeBakey　III　aortic　dissection,　patient-specific　models　of　DeBakey　III　aortic　dissection　treated　with　different　bypassing　strategies　were　constructed.　One　of　the　bypassing　strategies　is　bypassing　between　ascending　aorta　and　abdominal　aorta,　and　the　other　is　bypassing　between　left　subclavian　artery　and　abdominal　aorta.　Numerical　simulations　under　physiological　flow　conditions　based　on　fluid-structure　interaction　were　performed　using　finite　element　method.　The　results　show　that　blood　flow　velocity,　pressure　and　vessel　wall　displacement　of　false　lumen　are　all　reduced　after　bypassing.　This　phenomenon　indicates　that　bypassing　is　an　effective　surgery　for　the　treatment　of　DeBakey　III　aortic　dissection.　The　effectiveness　to　cure　through　lumen　is　better　when　bypassing　between　left　subclavian　artery　and　abdominal　aorta,　while　the　effectiveness　to　cure　blind　lumen　is　better　when　bypassing　between　ascending　aorta　and　abdominal　aorta.