Objective:To investigate the clinical value of ankle-brachial index (ABI) in evaluating vascular cognitive dysfunction (VCI) in the elderly.Methods:According to the mini mental state examination (MMSE) and Montreal cognitive assessment (MoCA), 200 elderly inpatients from May 2016 to February 2018 in our hospital were selected. MoCA scale was used to evaluate the cognitive function of the patients. The patients were divided into cognitive dysfunction group ( n=110) and cognitive normal group ( n=90). The clinical data of the two groups were analyzed and compared. The correlation between ABI and MMSE, MOCA and clinical indicators was observed. The receiver operating characteristic (ROC) curve of ABI value to the predictive value of VCI in the elderly was drawn. Results:⑴ There was no significant difference between the two groups in terms of gender, the first fasting blood glucose value in hospital and the situation of diabetes, hypertension and hyperlipidemia ( P>0.05); there was significant difference in age, low-density lipoprotein cholesterol (LDL-C) level, history of small cerebral vessels and ABI between the two groups ( P<0.05). ⑵ Logistic regression analysis showed that ABI was the related factor of VCI in the elderly ( P<0.01). ⑶ Pearson correlation analysis showed that MMSE score was positively correlated with ABI ( r=0.887, P<0.01), MOCA score was positively correlated with ABI ( r=0.843, P<0.01). ⑷ The area under ROC curve of ABI prediction value for VCI in the elderly was (0.965±0.01) [95% CI (0.945, 0.985), P<0.01]. When ABI ≤0.9, the sensitivity and specificity were 88.2%, 91.1% respectively; the accuracy and the yordan index were 89.5% and 0.793. Conclusions:⑴ ABI is an influencing factor of VCI in the elderly and is positively correlated with the severity of cognitive impairment in patients. ⑵ ABI has a high predictive value for VCI of the elderly, and ABI≤0.9 can be used as an early warning factor for VCI of the elderly.