Preeclampsia complicates 5-10% of pregnancies and is a leading cause of maternal/fetal morbidity and mortality. Although the cause is unknown, the reduced migration/invasion of extravillous trophoblasts is generally regarded as a key feature of preeclampsia genesis. The present study examined the expression of activator protein-2α (AP-2α), tissue inhibitor of metalloproteinase 2 (TIMP-2), matrix metalloproteinase-2 (MMP-2), matrix metalloproteinase-9 (MMP-9), and E-cadherin in severe preeclamptic placentas and normal placentas using real-time PCR and immunohistochemistry. The expression levels of AP-2α, TIMP-2, and E-cadherin were elevated, while MMP-2 and MMP-9 levels were decreased in severe preeclamptic placentas when compared with normal placentas. To explore the underlying molecular mechanisms, BeWo cells were transfected with an AP-2α-expression construct as well as a siRNA against AP-2α. The over-expression of AP-2α decreased the invasive abilities of BeWo cells. AP-2α induction was followed by the induction of TIMP-2 and E-cadherin and a significant reduction of MMP-2 and MMP-9. Whereas in AP-2α-silencing BeWo cells, we observed the decreased expression of TIMP-2 and E-cadherin and the increased expression of MMP-2 and MMP-9. We presume that AP-2α may suppress trophoblast invasion by repression of MMP-2 and MMP-9 and up-regulation of E-cadherin, thus leading to shallow placentation in severe preeclampsia.