Angiogenesis,a critical pattern of new blood vessel formation has been acknowledged as a main process from wound healing to tumor growth and metastasis.Many signaling pathway participates in this process including Notch signaling.However the mechanism of Notch signal regulating still is a tip of the iceberg.A current concept suggests that reactive oxygen species (ROS) can also promote cell signaling pathways triggered by growth factors and transcription factors that ultimately regulate cell behaviour such as poliferation and migriation.Is Notch signal also a member of them?In this study,we found that:1)Notch signal blockade in HUVECs leads to increased proliferation through up regulating ROS level; 2)Notch signal blockade promotes the closure of a scratched wound in HUVECs via a ROS-mediated mechanism; 3) Intracellular ROS production accelerates Notch inhibition-induced adhension of HUVECs; 4) ROS generation influences the tube formation of HUVECs provoked by Notch inhibition; 5)Inhibiting Notch signaling in HUVECs leads to increased intracellular ROS generation; 6) The intracellular ROS is produced by NADPH oxidase in HUVECS; 7) Disruption of Notch signal leads to up-regulation of Nox4 in HUVECs.These data suggest that the Notch signaling may function through regulating the intracellular ROS generation in endothelial cells.