Abstract: Objective：To evaluate the significance of Barthel index (BI) in elderly acute coronary syndrome (ACS) patients undergoing percutaneous coronary intervention (PCI). Methods：One hundred and eighty one elderly ACS patients undergoing PCI were divided into three groups based on BI: group A (BI＜70，n=62), group B (BI≥70- 90, n=72), and group C (BI≥90, n=47). The clinical characteristics and outcomes within one month after hospitalization were compared among 3 groups. Results：Compared with group C, patients in group A were older, with higher proportion of women, lower systolic blood pressure, higher white cell count, higher rates of previous peptic ulcer, higher proportion of ST- segment elevated myocardial infarction and emergency PCI (all P<0.05). In terms of clinical outcomes, patients in group A had lower left ventricular ejection fraction, higher pro- brain natriuretic peptide, more gastrointestinal bleeding events, and longer hospital stay. There was no significant difference between group B and group C in clinical characteristics and outcomes. Conclusions：Elderly patients with ACS and BI less than 70 had poor clinical outcome within one month after hospitalization. The risks and benefits for these patients should be carefully weighed when considering the coronary intervention.