Objective:　To　investigate　the　mechanical　mechanism　of　bypass　graft　for　the　treatment　of　DeBakey　III　aortic　dissection　and　explore　the　valid　surgical　planning.　Methods:　Patient-specific　models　of　DeBakey　III　aortic　dissection,　including　the　models　of　through　lumen　and　blind　lumen,　before　and　after　bypassing　between　ascending　aorta　and　abdominal　aorta,　between　left　subclavian　artery　and　abdominal　aorta,　were　constructed,　and　then　numerical　simulations　were　performed　using　computational　fluid　dynamics　(CFD)　method　under　physiological　flow　conditions　based　on　fluid-structure　interaction　(FSI).　Results:　Blood　flow　velocity,　pressure,　vessel　wall　displacement　of　the　false　lumen　after　bypass　graft　were　reduced　by　38.86%,　15.347　kPa　and　39.46%　on　average,　respectively.　Conclusions:　Bypass　graft　is　an　effective　surgical　method　for　the　treatment　of　DeBakey　III　aortic　dissection　under　specific　conditions　with　good　prospects　in　clinical　application.