Abstract: Objective To investigate the apoptosis in ECV304 induced by zinc oxide(ZnO) nanoparticles and the role of reactive oxygen species(ROS) in apoptosis.Methods Cell phagocytic effect was detected using crystal violet staining.Cell inhibition rate was detected by thiazolyl blue tetrazolium bromide(MTT) assay.The rate of DNA damage was detected by DNA ladder gel electrophoresis.The superoxide dismatase(SOD) and malondialdehyde(MDA) were detected by UV spectrophotometer.The ROS was detected by 2',7'-dichlorofluorescein-diacetate(DCFH-DA) fluorescent probe.Results ZnO nanoparticle entered ECV304 cell through phagocytosis and distributed in cluster.The values of MTT in different dose groups(0.85±0.04,0.56±0.03,0.51±0.05,and 0.45±0.044) were significantly different from that of the control group (P< 0.01).The levels of ROS in different dose groups (33.14±0.38,35.82±0.61,54.13±0.24,and 68.81±1.24) were significantly higher than that of the control group(30.12±1.23,P< 0.01).The levels of SOD in different dose groups(25.72±0.48,25.64±0.36,25.53±0.36,and 25.25±0.44) were significantly lower than that of the control group(26.39±0.40,P< 0.01).The levels of MDA in different dose groups were significantly higher than that of the control group(0.56±0.01,P< 0.01).The cell apoptosis of alpha hipoic acid(LA) group was significantly low er than those of treatment groups.Conclusion Nano-ZnO can inhibit ECV304 cell proliferation,induce apoptosis through ROS pathw ay,and produce cytotoxicity.