Aim To study the flow mediated dilation (FMD) of brachial artery at different time points before and after parturition in patients with severe preeclampsia. Methods 49 cases of severe preeclampsia (study group) were examined by high-frequency color Doppler ultrasonography before parturition (28-40 weeks of pregnancy), and 1,6, 24 weeks after parturition, and the right brachial artery FMD was detected. 60 cases of healthy childbearing women was as the control group. The internal diameter (D1) and blood flow (Q1) of right brachial artery, and the internal diameter (D2) and blood flow (Q2) after reactive hyperemia were measured at resting state. The vessel diameter change rate (△D%) and the blood flow change rate (△Q%) were calculated. Results Before parturition, and at different time points (1,6, 24 weeks) after parturition, the △D% and △Q% of the study group were lower than those of the control group (P＜0.001). There were no significant differences in △D% and △Q% inside the study group before parturition, and at different time points after parturition (1,6, 24 weeks) (P＞0.05). Conclusion Patients with severe preeclampsia have FMD damage before parturition and continue to post parturition, and there is no obvious recovery and improvement for the 24 weeks after parturition.