Objective:To investigate the effect of extract of Juglans mandshurica maxim on apoptosis of endothelial cells induced by endogenous H,2,O,2, in vitro  Methods:Endothelial cells induced by endogenous H,2,O,2, cells were cultured by incubating with 10 mU GOX. ① Cells were divided into the blank control group, 10 mU GOX group, and experimental groups by different concentrations (10 mU GOX and 25 mg/L, 50 mg/L, 100 mg/L extract). Each group was treated with the corresponding measures. The effect of Juglans mandshurica maxim on morphology and proliferation of vascular endothelial cells were detected. ② Cells were divided into the blank control group, 10 mU GOX group and 10 mU GOX+50 mg/ L extract group, and each group was treated with the corresponding measurements. The apoptotic cells were detected by Hoechst 33258 Assay Kit, and apoptotic percent was measured by flow cytometry (FCM) after Annexin / PI double staining  Results: ① Compared with the blank control group, there were significant differences in the cell survival rate in the 10 mU GOX group, 10 mU GOX+25 mg/L, 50 mg/L and 100 mg/L groups (P＜0.05, P＜0.01). The cell survival rates in the 10 mU GOX+25 mg/L, 50 mg/L and 100 mg/L groups were higher than that of the 10 mU GOX group (P＜0.05, P＜0.01).   Results: of Hoechst33258 fluorescence staining showed that:compared with the blank control group, apoptosis rate in the 10 mU GOX group was increased significantly (P,<,0.01); compared with the 10 mU GOX group, apoptosis rate in the 10 mU GOX+50 mg/L group was increased markedly (P,<,0.01)  Conclusion:The extract of Juglans mandshurica maxim can protect the cells significantly, which indicate that it has inhibiting effect on cell apoptosis induced by endogenous H,2,O,2,.