Abstract： Objective The purpose of this study was to use a high flow grafts bypass for giant and complex aneurysms. Method 39 patients with complex aneurysms were treated with use of graft bypass. 11 patients presented with subarachnoid hemorrhage referred to lower Hunt and Hess grade Ⅰ and Ⅱ , and 28 patients with unruptured aneurysms exhibited their headaches, symptom and signs of mass effect and neural compression, and cerebral ischemic deficits. 13 patients were bypassed with the radical arteries(RAG) ,10 patients were bypassed with the saphenous veins(SV) ,10 patients were interposed with superficial temporal arteries ( STA ) , and 6 patients were bypassed with the occipital arteries ( OA) . The graft vessel were anastomosed to the recipient of the middle cerebral artery ( MCA) in 24 cases, the PICA in 5 cases, the posterior cerebral artery in 4 cases, the anterior cerebral artery (ACA) in 2 cases, the vertebral artery ( V5) in 2 cases, the intracranial carotid arteries in 1 case, inferioanterior cerebellar artery in 1 case. The graft vessel were anastomosed with the donor external carotid arteries in 19 cases, the MCA in 8 cases, the ACA in 2 cases, vertebral artery(V3) in 2 cases, internal carotid arteries(C2) in 1 case, proximal A2 portion of the posterior communicating artery in 1 case, additional to 6 cases with the OA bypass without anastomosis of recipient vessel. The aneurysms were trapped after the graft had been completed in the series. Excision of aneurysm was carried out in 19 patients with mass effect and neural compression. Results 35 patients obtained back to their normal life, three patient needs to assist for his daily life and one death occurred related to the brain stem infarction. 35 patients were received the postoperative angiographies underwent,34 patients were confirmed with patency of the bypass graft and elimination of the aneurysms on angiographies, but one patient was unidentifiable with patency of the bypass graft on angiography. Conclusions Bypass graft should be an effective management for surgical treatment of giant or complicated aneurysms.