Placentation, which is critical for maternal-fetal exchange of nutrients and gases, is a complicated process comprising stepwise vasculogenesis and angiogenesis. Hypoxia caused by impaired trophoblast invasion may cause various angiogenic abnormalities in human placenta. The Notch1 signaling pathway plays an important role in the regulation of angiogenesis. The angiogenesis of human umbilical vein endothelial cells(HUVECs) under normal/hypoxic conditions and the m RNA/protein level of Notch1/Dell4/Jagged1 were investigated in this study. The effects of DAPT/JAG-1 on the migration of HUVECs were also assessed by cell wound healing assay, so as to discover the possible role of notch1 signaling pathway in the angiogenesis of human placenta. The results showed that angiogenic ability of HUVECs was seriously reduced under hypoxic conditions. The m RNA and protein levels of Notch1/Dell4/Jagged1 were decreased in the hypoxic group compared to the control one. In addition, the migration capability of HUVECs was significantly obstructed when treated with DAPT and under hopoxic condition, but promoted when treated with JAG-1. The above results demonstrate that hypoxia downregulates the angiogenesis in human placenta via Notch1 signaling pathway. Placentation, which is critical for maternal-fetal exchange of nutrients and gases, is a complicated process that includes stepwise vasculogenesis and angiogenesis. Hypoxia caused by impaired trophoblast invasion may cause various angiogenic abnormalities in human placenta. The Notch 1 signaling pathway plays an important role in the regulation of angiogenesis. The angiogenesis of human umbilical vein endothelial cells (HUVECs) under normal / hypoxic conditions and the m RNA / protein level of Notchl / Dell4 / Jaggedl were investigated in this study. The effects of DAPT / JAG-1 on the migration of HUVECs were also assessed by cell wound healing assay, so as to discover the possible role of notch1 signaling pathway in the angiogenesis of human placenta. The results showed that angiogenic ability of HUVECs was seriously reduced under hypoxic conditions. The m RNA and protein levels of Notch1 / Dell4 / Jagged1 were decreased in the hypoxic group compared to the control one. In addition, the migration capabi lity of HUVECs was significantly obstructed when treated with DAPT and under hopoxic condition, promoted when treated with JAG-1. The above results demonstrate that hypoxia downregulates the angiogenesis in human placenta via Notchl signaling pathway.