Objective:To investigate the influencing factors for prognoses of patients with high-grade aneurysmal subarachnoid hemorrhage (aSAH).Methods:A retrospective analysis was performed on clinical data of 104 patients with aSAH, admitted to our hospital from January 2012 to March 2010. According to the modified Rankin scale (mRS) scores 3 months after discharge, these patients were divided into good prognosis group (mRS scores≤2) and poor prognosis group (mRS scores >2). Clinical data of patients from the 2 groups were compared. Multivariate Logistic regression analysis was used to analyze the influencing factors for prognoses.Results:Forty patients (38.5%) were with good prognosis and 64 (61.5%) were with poor prognosis. As compared with patients in the poor prognosis group, patients in the good prognosis group had significantly lower proportion of patients>60 years old, and significantly lower Graeb scores, cast fourth ventricle (CFV) incidence, Fisher grading, blood glucose content, diastolic blood pressure, systolic blood pressure and mean arterial pressure, and statistically higher serum potassium content ( P<0.05). There were significant differences in treatment methods and incidence of complications between the two groups ( P<0.05). Multivariate Logistic regression analysis showed that age>60 years ( OR=13.470, 95%CI: 2.177-83.347, P=0.005), Fisher grading ( OR=6.649, 95%CI: 1.141-38.736, P=0.035), conservative treatment ( OR=6.348, 95%CI: 1.048-38.742, P=0.044), mean arterial pressure at admission ( OR=29.721, 95%CI: 3.177-278.012, P=0.003), serum potassium ( OR=5.296, 95%CI: 1.138-24.653, P=0.034), CFV ( OR=9.855, 95%CI: 1.785-51.456, P=0.008), and chronic hydrocephalus ( OR=19.298, 95%CI: 3.294-113.069, P=0.001) were influencing factors for prognoses of high-grade aSAH patients. Conclusion:Severe aSAH patients with advanced age, high Fisher grading, high mean arterial pressure, low serum potassium content, fourth ventricle casting and chronic hydrocephalus under conservative treatment are more likely to have poor prognosis.