The close relationship between aging and endothelial dysfunction points to a critical need to find ways to protect against endothelial senescence. Ginsenosides are a class of steroid glycosides found exclusively in the plant genus, panax. Much evidence has demonstrated that ginseng generates beneficial effects on health. In the United States of America, ginseng ranks second and fifth among the 10 most common natural products used by adults in 2002 and 2007, respectively. Ginsenosides are divided into two groups: Rb1 group and Rg1 group. Ginsenoside Rb1 is one of the most abundant ginsengs and also attracts much attention. Rb1 affects the reproductive system and embryo development. Recently, an increasing amount of evidence has demonstrated that Rb1 could increase endothelial nitric oxide synthase and reverse H2O2- or homocysteine-induced endothelial dysfunction in vivo and in vitro. Sirtuin-1 is an NAD+ -dependent lysine deacetylase, and it has been recognized to play important roles in cell aging, organism longevity, and stress responses. Sirt1 increased eNOSderived nitric oxide through the deacetylation of eNOS. H2O2 treatment reduces its expression in human lung epithelial cells and causes a dose-dependent reduction in human endothelial cells. Our previous studies have shown that Rb1 prevented HUVEC senescence through modulating redox status. However, it is unknown whether Sirt1 is involved in Rb1 prevention of H2O2- induced HUVEC senescence. The present study provides evidence to support the novel role of Sirt1 in the prevention of the Rb1 effects on HUVEC senescence. In this study, we found that 60 mmol/L of H2O2 effectively induced premature senescence of the HUVECs without any apparent apoptosis. Rb1 protected the HUVECs from an H2O2- induced senescence through the stimulation of Sirt1 pathway. An increased Sirt1 expression decreased the acylation of eNOS in senescent HUVECs in order to produce more NO. In both animal and human experiments, vascular oxidative stress develops with age. During in vitro experiments, oxidative stressors such as H2O2 and ox-LDL can drive cell senescence. As a disease model induced in primary cells is more clinically and physiologically relevant to human disease, the primary HUVECs are ideal for use in studying endotheliumrelated diseases. Hence, we chose a premature H2O2-induced senescence of HUVECs to perform our experiments. As for the senescence model, 30–100 mmol/L of H2O2 was reported to be efficient in inducing senescence in HUVECs. This is in agreement with our results. However, if 80 or 100 mmol/L of H2O2 was used, there were few cells left, along with an apoptotic trend. In order to exclude the effect of apoptosis in our results, we established a senescence model with 60 mmol/L of H2O2. SIRT1 has been increasingly recognized in playing a critical role in cellular senescence and aging. As a person’s age ALK5 Inhibitor II increases, the mRNA level of Sirt1 decreases in endothelial cells obtained from a patient’s saphenous vein that was harvested during a bypass surgery. In fact, it has been reported that the endothelial cells in samples of a human atherosclerotic aorta exhibited a senescent-like phenotype, along with an increased expression of PAI-1 and SA-b-gal activity.