Abstract: Objective　To investigate the protective effect of ginsenoside Rg3 on hydrogen peroxide (H2O2)-induced injury of human ovarian granulosa cells KGN, and to explore its possible mechanism. Methods　KGN cells were cultured and then stimulated with different concentrations of H2O2 for 2 hours to establish a model of oxidative damage in KGN cells. Ginsenoside Rg3 pretreated for 24 h followed by stimulation with H2O2. CCK-8 kit was used to detect the cell viability and to screen the effective concentration. KGN cells were divided into 4 groups, control group, H2O2 model group, H2O2+Rg3 group and Rg3 group. The level of intracellular reactive oxygen species (ROS) was detected by DCFH-DA fluorescent probe. AnnexinⅤ/PI double staining and flow cytometry were used to detect the effect of ginsenoside Rg3 on the apoptosis of KGN cells induced by H2O2. Western blot assay was used to detect apoptosis-related proteins BAX and Bcl-2 and the expression of cytochrome C. Results　Compared with the control group, the cell viability decreased in the H2O2 model group, the ratio of apoptosis increased (P＜0.01), the level of ROS increased, the level of cytochrome C increased significantly, and the ratio of Bcl-2/BAX decreased (P＜0.05). Compared with the model group, ginsenoside Rg3 pretreatment for 24 h can significantly increase the cell viability, reduce excessive ROS production, reduce the proportion of apoptotic cells, reduce the level of cytochrome C and increase the expression of Bcl-2/BAX (P＜0.05). There were no significant differences in the above indicators between the control group and Rg3 group. Conclusion Ginsenoside Rg3 preconditioning has a significant protective effect on H2O2-induced oxidative damage in KGN cells, which is related to slowing down ROS excessive accumulation and inhibiting mitochondrial apoptosis pathway.