This study is to investigate the effect of miRNA-24 on endothelial nitric oxide synthase (eNOS) expression and vascular endothelial cell proliferation. Constructed high expression miRNA-24 plasmids were introduced into human umbilical vein endothelial cells (HUVECs) by liposome. Cell numbers were counted by a Hemocytometer, and cell proliferation was detected by MTT assay. The expression levels of eNOS and specificity protein 1 (Sp1) at mRNA and protein levels were, respectively, examined by real-time PCR, immunohistochemistry, and Western blotting. Compared with the control group, endothelial cell proliferation in miRNA-24 group significantly decreased by 64.24 % (6.53 ± 0.11 vs 18.26 ± 0.45, P < 0.01). The expression of eNOS at mRNA and protein levels in miRNA-24 group decreased by 64.21 % (0.34 ± 0.01 vs 0.95 ± 0.02, P < 0.05) and 82.86 % (0.072 ± 0.06 vs 0.42 ± 0.06, P < 0.05), respectively. Meanwhile, the expression of Sp1 at mRNA and protein levels in miRNA-24 group decreased by 64.64 % (0.35 ± 0.01 vs 0.99 ± 0.03, P < 0.05) and 60.34 % (0.23 ± 0.05 vs 0.58 ± 0.07, P < 0.05), respectively. In anti-miRNA-24 group, endothelial cell proliferation decreased by 33.46 % compared with the control group (12.15 ± 0.21 vs 18.26 ± 0.45, P < 0.01), while it increased by 46.25 % compared with the miRNA-24 group (12.15 ± 0.21 vs 6.53 ± 0.11, P < 0.01). The expression of eNOS at mRNA and protein levels in anti-miRNA-24 group decreased by 44.21 % (0.53 ± 0.04 vs 0.95 ± 0.02, P < 0.05) and by 30.95 %(0.29 ± 0.05 vs 0.42 ± 0.06, P < 0.05) compared with the control group, while it increased by 35.84 % (0.53 ± 0.04 vs 0.34 ± 0.01, P < 0.05) and by 75.17 % (0.29 ± 0.05 vs 0.072 ± 0.06, P < 0.05) compared with miRNA-24 group. The expression of Sp1 at mRNA and protein levels in ant-miRNA-24 group decreased by 36.36 % (0.63 ± 0.04 vs 0.99 ± 0.03, P < 0.05) and by 22.41 % (0.45 ± 0.06 vs 0.58 ± 0.07, P < 0.05) compared with the control group, while it increased by 44.44 % (0.63 ± 0.04 vs 0.35 ± 0.01, P < 0.05) and by 48.88 % (0.45 ± 0.06 vs 0.23 ± 0.05, P < 0.05) compared with miRNA-24 group. HUVECs proliferation and eNOS expression are significantly inhibited by miRNA-24. Sp1, which is regulated by miRNA-24, might act as one of the important factors involved in eNOS gene expression.