Abstract： Objective To evaluate and summarize the possibility and experience of extra-intracranial (FC-IC) high flow bypass using saphenous vein graft for the treatment of intracavernous sinus aneurysms. Method A segment of saphenous vein was dissected and prepared for use,then exposure the extra and intracaroted artery in neck and performed pterinai approach to exposure the M1 and M2 segment in middle cerebral artery or internal carotid artery in supra-clinoid process,a saphenous vein graft is used as the bypass conduit. Results 4 cases were demonstrated the patency of the grafts in the postoperative angiography or CTA, 4 cases with the symptom of headache were disappeared postoperatively and 2 cases with the decreased visual acuity were improved greatly. One patient occurred postoperatively in the state of coma due to the acute thrombosis of the implanted saphenous vein and died of lung infection at the 10th day after operation. Conclusions Extra-intracranial (EC-IC) high flow bypass using saphenous vein graft is an effective approch for the treatment of giant intracavemous sinus aneurysms. It is necessary to keep strictly the operative indication to decrease the operative risk by evaluation of the hemadynamical state prior to the surgery.