Objective: To investigate the effects and potential mechanisms of metformin on the inflammatory cytokine IFN-γ induced cell damage in human ovarian granulosa cell KGN. Methods: The effects of of metformin alone and with IFN-γ on the viability of KGN cell were detected using CCK-8 kit and the cell growth status of KGN cell were observed under microscope. The apoptotic cells and the cell cycle in KGN cell were analyzed using Flow Cytometry. The mRNA expression levels of (Cyclin Dependent Kinase Inhibitor 1A,CDKN1A) , a gene related to cell cycle regulation, were analyzed using q-PCR. Results: IFN-γ treatment inhibited the vitality of KGN cellthrough blocking these cells from G0-G1 phase to S phase and promoting into apoptosis. Although metformin treatment alone had no obvious effects on the KGN cells, ititalleviated the apoptosis in KGN cell and reversed the cell cycle which induced by IFN-γ. Moreover, metformin significantly inhibited the the expression levels of CDKN1A in IFN-γ treated KGN cell. Conclusion: Metformin had a protective role on the IFN-γ induced cell injury in KGN cell by by down-regulating the abnormal expression of the negative cell cycle regulator CDKN1A in these cells．