Objective: To explore the effect of Sirt1 on the function of endothelial progenitor cells (EPCs) in rats with chronic obstructive pulmonary disease (COPD). Methods: A rat COPD model was established via smoking and endotoxin administration for three months. The peripheral circulating EPCs were isolated by gradient centrifugation, and their functions, cell cycle distribution, apoptosis, and Sirt1 expression were examined. The function changes of EPCs in the presence or absence of Sirt1 agonist and inhibitor were estimated; meanwhile, the expressions of Sirt1, FOXO3a, NF-κB, and p53 were also evaluated. Results: The proliferation, adhesion, and migration of EPCs decreased while the apoptosis rate was increased in the COPD rats. The expression of Sirt1 protein in EPCs of the COPD group was significantly lower than that in the control group (P