Preeclampsia (PE) is a principal cause of maternal and newborn mortality that poses financial and physical burdens to tens of thousands of families each year. Unfortunately, there is no effective management to arrest the progression of this disease unless delivery. Therefore, standardized management or preventive treatments are needed urgently. PE is closely associated with placental hypoxia, which increases the secretion of soluble fms-like tyrosine kinase 1 (sFlt-1) as well as soluble endoglin (sEng) into the maternal circulation. Metformin has been found to inhibit those anti-angiogenic factors so it might be a candidate to prevent or treat PE. Women who are diagnosed with gestational diabetes mellitus (GDM) are more likely to have complications of hypertension or PE, so this review aims to demonstrate that the application of metformin in GDM might prevent the onset or progression of PE complicated with GDM.