Aim To investigate the relationship between carotid stenosis and endothelial progenitor cells (EPC) and the regulation of insulin-like growth factor-1 (IGF-1) on EPC and its mechanism. Methods 35 patients with cerebral infarction and carotid stenosis were enrolled into the carotid stenosis group. At the same time, 11 healthy control subjects were selected as control group. According to the results of cerebral angiography, carotid stenosis group was divided into 3 subgroups: mild stenosis group, middle stenosis group, severe stenosis group. The serum IGF-1 concentration of the study subjects was determined. Mononuclear cells were isolated by density gradient centrifugation and cultured with endothelium growth medium 2 (EGM2), and the double staining method was used to identify EPC. The experiment was divided into 4 groups:untreated group, IGF-1 group, IGF-1＋NG-nitro-L-arginine methyl ester (L-NAME) group and L-NAME group. Cells were cultured with EGM2 for 2 to 3 weeks, and the proliferation and adhesion function of EPC were determined in each group. Results The more severe the degree of carotid stenosis, the lower the number of EPC colony forming (P＜0.05), the lower the serum IGF-1 concentration, and the proliferation and adhesion ability of EPC decreased with the increase of the degree of stenosis. Function experiments showed that EPC function in IGF-1 group was significantly higher than that in untreated group (P＜0.01), IGF-1＋L-NAME group had no obvious difference, and EPC function in L-NAME group was lower than that in untreated group. The endothelial nitric oxide synthase (eNOS) in IGF-1 group was significantly higher than that in untreated group, there was no significant difference in IGF-1＋L-NAME group, and eNOS in L-NAME group was lower than that in untreated group. Conclusion EPC may have a protective effect on carotid stenosis, and IGF-1 may enhance the function of EPC by affecting the synthesis of eNOS.