Objective To study the advantages and disadvantages of aneurysm surgery with different timing in a two -year period.Methods This study examined 449 patients with ruptured intracranial aneurysms treated surgically between Dec 2008 and Dec 2010 in Department of Neurosurgery,2nd affiliated hospital of Zhejiang University Medical Institute.Early aneurysm surgery was defined as operation performed within 72 hours after onset of subarachnoid haemorrhage; non - early surgery as performed after 72 hours.Muhiple factors,including the incidence of pre -operative rebleeding,incidence of complete occlusion of the ruptured aneurysm and incidence of major complications such as cerebral infarction and hydrocephalus,were analyzed.Surgical outcomes after 3 months were assessed using the Glasgow outcome score (GOS).Survival analysis was used to analyze 3 months follow - up date with outcome events as death,cerebral infarction or hydrocephalus. Patients were categorize into 2 subgroups grading by the Hunt - Hess classification,that was,one subgroup of patients with Hunt - Hess grades Ⅰ,Ⅱ and Ⅲ and the other subgroup of patients with grades Ⅳ and Ⅴ Multiple factors of the two subgroups were analyzed.Results 50.1％ of cases fell into the early surgery group and 49.9％ into the non - early operated group.There was a lower rate of pre - operative rebleeding in the early surgery group (5.36％ versus 1.33％,P ＜ 0.05 ).The incidence of complete occlusion of the ruptured aneurysm and the incidence of major complications showed no significant difference between these 2 groups.There was no significant difference in GOS between the early surgery group and the non - early surgery group at 3 months.In the subgroup of patients with Hunt - Hess grades Ⅰ,Ⅱ and Ⅲ,there was a lower rate of pre - operative rebleeding in the early surgery group ( 3.98 versus 0.4.9％,P ＜ 0.05 ) and there was no significant difference in other factors.In the subgroup of patients with Hunt - Hess grades Ⅳ and Ⅴ,there was no significant difference in all factors.Conclusions Early operation,especially for the patients with Hunt - Hess grades Ⅰ,Ⅱ and Ⅲ,can significantly reduce the rebleeding before surgery.The timing of surgery do not significantly affect incidence of surgical complications and surgical outcomes.