Abstract：Objective：To investigate the effects of scallion extract on the activity，apoptosis and oxidative stress of brain microvascular endothelial cells treated with hydrogen peroxide(H2O2) and its possible mechanism. Methods： Rat brain microvascular endothelial cells(RBMEC) were cultured in vitro. RBMEC was treated with H2O2 to establish the cell damage model. Different doses of scallion extract were added to treat the cells. pcDNA and pcDNA- CAI2 were transfected into RBMEC respectively. Scallion extract and H2O2 were added to treat the cells together；MTT assay and flow cytometry were used to detect cell activity and apoptosis rate. The expression of long chain noncoding RNA CAI2(LncRNA CAI2) was detected by real- time fluorescence quantitative polymerase chain reaction(qRT- PCR). The activity of LDH was detected by 2，4- dinitrophenylhydrazine colorimetry. The activity of SOD was detected by xanthine oxidase method.The expressions of Cleaved- caspase3， Bax， Pro- caspase3 and Bcl- 2 were detected by Western blot. Results： Compared with con group， H2O2 treatment could significantly reduce cell activity， SOD activity， Pro- caspase3 and Bcl- 2 protein levels(P＜0.05)， increase CAI2 expression level，apoptosis rate，LDH activity and Cleaved-caspase3 and Bax protein levels(P＜0.05). Scallion extract could significantly reverse the effects of H2O2 on RBMEC activity， apoptosis rate， oxidative stress and CAI2 expression.Compared with H2O2 + scallion high + pcDNA group，the cell activity，SOD activity and Pro- caspase3 and Bcl- 2 protein levels in H2O2 + scallion high + pcDNA- CAI2 group decreased(P＜0.05)， and the apoptosis rate， LDH activity and Cleaved- caspase3 and Bax protein levels increased significantly(P＜0.05). Conclusion： Scallion extract can enhance the activity of RBMEC induced by H2O2，inhibit cell apoptosis and oxidative stress，and then protect RBMEC cells from damage by inhibiting the expression of CAI2.