Objective To investigate the characteristics of cognitive impairment and related risk factors in elderly patients with aneurysmal subarachnoid hemorrhage (aSAH). Methods A total of 106 elderly patients with aSAH admitted to Shunyi District Hospital and Tiantan Hospital in Beijing from December 2012 to December 2017 were recruited and assigned to the aSAH group, and 120 normal patients in Neurology Outpatient Department during the same period were collected as the control group. The patients in aSAH group were assessed with neuropsychological scales at admission, discharge, and 3,6 and 12 months after discharge, and those in control group were assessed with neuropsychological scales at consultation. The cognitive function was assessed by the Beijing version of the mini-mental state examination (MMSE) scale, and corrected by the revised Hasegawa intelligence scale and the simple screening scale for dementia. SPSS statistics 17.0 was used for data processing. According to the data type, Chi-square test or Student′s t test was employed for comparison among groups. Multivariate logistic regression analysis was applied to screen independent risk factors. Results There was significant difference in the scores of MMSE between aSAH group and control group [(23.51±1.20) vs (27.01±3.72), P<0.05]. The highest incidence of cognitive impairment was observed in the aSAH group in 3 months after discharge, with the lowest scores in the items such as executive ability, verbal comprehension and expressiveness, verbal naming ability, verbal retelling, attention and computational power, and short-term memory. Multivariate logistic regression analysis showed that the interventions (OR=1.667,5%CI 0.567-6.468; P=0.027), H-grade (OR=1.126,5%CI 0.518-2.755; P=0.002) and Fish-grade (OR=1.297,5%CI 0.477-1.982; P=0.028) of aneurysms were significantly correlated with cognitive impairment in the elderly.Conclusion Cognitive impairment after aSAH is more obvious in 3 months after onset, mainly in speech, executive ability, attention, calculation ability and short-term memory. Emphases should be paid in the evaluation of Fish and H grading in clinical practice. Early recognition of high-risk patients and early intervention for cognitive impairment can improve prognosis.