Abstract： Objective To explore the efficacy and safety of endovascular embolization of unruptured intracranial aneurysms (UIA).Methods We retrospectively analyzed the clinical outcomes and complications of 256 patients with UIA who underwent endovascular embolization at Department of Neurosurgery,Zhujiang Hospital,Southern Medical University from January 2011 to December 2016.The clinical prognosis was further evaluated by using modified Rankin Scale (mRS).Results In 256 patients (333 aneurysms),the percentage of complete occlusion after endovascular procedures was 88.7％ (227/256).Poor clinical outcomes were reported in 24 (9.4％) cases.Surgery-related complications occurred in 9 (3.5％) cases,out of which 3 (1.2％) showed hemorrhage and permanent neurological deficit was observed in 1 case(0.4％).Associated headaches following endovascular treatment occurred in 86 patients (33.6％),and were more commonly observed in cases undergoing stent assisted embolization of UIA (P =0.04).The mean follow-up time was 18.6 ± 1.5 months and ranged from 3 to 49 months.During the follow-up period,stent stenosis oecttrred in 6 patients (2.3％),10 patients (3.9％) developed recurrence of aneurysm,and no case died.Finally,favorable clinical prognosis (mRS ＜2) was achieved in 95.7％ of the patients.Patients with giant aneurysms (diameter over 25 mm) were more likely to achieve poor outcomes (P =0.045),and the diameter of UIA over 10 mm (P =0.004) was correlated with aneurysm recurrence after endovascular treatment.Conclusions Endovascular embolization is suggested to be a safe and efficacious way to treat UIA.Proper selection of surgical candidates could be helpful for reducing the risk of bleeding and achieving favorable outcome.