Objective To explore the expressions and functions of miR-155, miR-125b-5p, miR-210, and their target proteins, in vascular endothelial cells in oxidative stress. Methods Human umbilical vein endothelial cells (HUVECs) were isolated and cultured; the expression of endothelial cell factor VIII related antigen was detected by immunofluorescence staining; and the expression of CD31 was detected and identified by flow cytometry. The oxidative stress model of vascular endothelial cells was established by preeclampsia serum and hydrogen peroxide (H2O2) treatment. The treated HUVECs were divided into 4 groups: normal pregnancy serum group, preeclampsia serum group, 0 μmol/L H2O2 group and 100 μmol/L H2O2 group. The levels of miR-155, miR-125b-5p, and miR-210 were tested by real-time quantitative PCR within 24 hours after modeling. The expression of Smad4 protein was detected by Western blotting and immunofluorescence staining. Cell apoptosis was detected by flow cytometry combined with annexin V-FITC/PI staining. Results Compared with 0 μmol/L H2O2 group, miR-125b-5p significantly decreased in 100 μmol/L H2O2 group, while Smad4 protein significantly increased. In addition, 100 μmol/L H2O2 treatment promoted cell apoptosis and necrosis. Compared with normal pregnancy serum group, the apoptosis and necrosis were significantly enhanced in preeclampsia serum group, but there were no significant differences in miR-125b-5p and Smad4 between the groups. Conclusion High level of H2O2 up-regulates Smad4 protein expression and inhibits miR-125b-5p expression.