The aim of the present study was to characterize the role of microRNA (miR)-155 in the pathogenesis of severe preeclampsia (PE). A total of 19 severe preeclampsic and 22 normal placentas were collected to measure miR-155 and endothelial nitric oxide synthase (eNOS) expression using quantitative (q)PCR and western blot analysis. The results demonstrated a significant increase in the levels of miR-155 and decreased eNOS expression in the severe preeclampsic placentas, as compared with the normal controls. In order to examine the function of miR-155 in the human placenta, the HTR8/Svneo cell line was transiently transfected with an miR-155 mimic or its inhibitor, anti-miR-155. It was confirmed that miR-155 may suppress the expression of eNOS in HTR-8/SVneo cells. Furthermore, a transwell insert invasion assay demonstrated that miR-155 inhibited cell invasion in trophoblast cells, and the effect was rescued by over expression of eNOS. The present study revealed that miR-155 has a negative regulatory role in the migratory behavior of HTR-8/SVneo cells via modulating eNOS.