Objective To study of effects Medlar flavone on NO and NOS in H 2 O2 damaged vascular endothelial cells.Meth-ods Human Umbilical Vein Endothelial Cells(HUVEC)have been set as research object.HUVEC cells was damaged by H 2 O2 in-duced oxidative stress.Experiments were divided into normal control group,H 2 O2 injury group,VitC control group,and low,medi-um,high flavonoids protective groups(100,200,400 mg/L).MTT method was used to observe cells activity.The effects Medlar fla-vone on MDA、TNOS、iNOS and NO in H 2 O2 damaged vascular endothelial cells was observed.Results (1)MTT result demonstra-ted the IR of HUVEC cells was 38.8% in H 2 O2 injury group.Which in low,medium,high flavonoids protective groups were 34.0%,30.7%,25.5%.All were lower than H 2 O2 injury group(P <0.01).(2)Compared with normal control group,NOS activity was decreased in H 2 O2 injury cell,while TNOS,iNOS,NO was more.Compared H 2 O2 group,the change of NO,TNOS,iNOS, MDA was opposite in flavone intervention group,and which were dose dependent (P <0.01 ).Conclusion Medlar flavone has a protective effect on H 2 O2 induced HUVEC cells injury,and there may be some kind of relevance between them.