Objective To study the effects of three kinds of magnetic nanomaterials on reactive oxygen species, cell junction of vascular endothelial cells in vitro and their relationship. Methods Primary human umbilical vein endothelial cells (HUVECs) were randomly divided into control and magnetic nanoparticles exposed groups.Dynamic light scattering (DLS) was used to characterize the particle size and charge of nanomaterials. CCK-8 method was used to measure cell viability. Flow cytometrywas used to observe the level of ROS in cells by DCFH-DA fluorescent probe labeling. Using iron staining and transmission electron microscopy (TEM) to observe the uptake of magnetic nanomaterials by endothelial cells.The cells were fluorescently labeled with VE-cadherin antibody, and the cell junctions were observed under a laser confocal microscope. The expression of VE-cadherin was analyzed by western blot. Results Magnetic nanomaterials could increase ROS in endothelial cells, decrease VE-cadherin levels and the gap between cells increased. When treated with the antioxidant N-acetylcysteine, the level of reactive oxygen decreased, while the cell junction tends to be intact. The effects of magnetic materials on the activity of endothelial cells, ROS level, VE-cadherin expression were different due to components, surface modification, and size. Conclusions Different magnetic nanoparticles have different effects on the ROS and cell junction of endothelial cells; the exposure dose used in experiments can affect the integrity of endothelial cell junction.