Objective  To investigate the effect of calycosin on mitochondrial apoptotic pathway in oxygen-glucose deprivation/reoxygenation PC12 cells.    Methods  PC12 cells were randomly divided into four groups: control group, model group, calycosin group and nimodipine group. Except for the control group, the other groups were treated with oxygen and glucose deprivation for 2 hours and compound oxygen and glucose for 24 hours. Calycosin group and nimodipine group were treated with drug-containing medium containing calycosin (0.07 μmol/L) and nimodipine (5.00 μmol/L) simultaneously with reoxygenation. CCK-8 method  was used to detect cell survival rate, flow cytometry was used to detect cell apoptosis rate, immunofluorescence method  was used to detect Bax/Bcl-2 ratio, Western blotting was used to detect the expression of key proteins cytochrome C(Cyt-C), apoptotic protease activating factor-1(Apaf-1) and Caspase-3 in mitochondrial apoptotic pathway.   Results Compared with the control group, the survival rate of cells in model group decreased significantly (P<0.05), and the apoptotic rate increased significantly (P<0.05), the ratio of Bax/Bcl-2 was significantly increased (P<0.05), and the expression of key proteins Cyt-C, Apaf-1 and Caspase-3 in mitochondrial apoptotic pathway were significantly increased (P<0.05). Compared with the model group, the cell survival rates of calycosin group and nimodipine group increased significantly (P<0.05), apoptotic rate decreased significantly (P<0.05), the ratio of  Bax/Bcl-2 was significantly decreased (P<0.05), and the expression of key proteins of mitochondrial apoptotic pathway, Cyt-C, Apaf-1 and Caspase-3 were significantly decreased (P<0.05). The difference has statistical significance.   Conclusion  Calycosin can significantly improve the survival rate of oxygen-glucose deprivation/reoxygenation PC12 cells and inhibit cell apoptosis. Its mechanism is closely related to the inhibition of the expression of key proteins Cyt-C, Apaf-1 and Caspase-3 in mitochondrial apoptotic pathway by calycosin.