【Objective】 To explore the effect of Genistein on the proliferation and cell cycle regulation of ovarian cancer cells. 【Methods】 Ovarian cancer OVCAR-5 cells were treated with Genistein. Cell counting and MTS assays were performed to determine the alterations of cell proliferation. Real-time PCR and Western blotting were conducted to examine the expression changes of key cell cycle regulators. 【Results】 Genistein significantly promoted the proliferation and viability of OVCAR-5 cells. After Genistein treatment, cellular mRNA and protein expression levels of cell cycle activators such as PCNA, Cyclin D1 and CDK4 were increased, but those of cell cycle inhibitors such as p21 and p27 were decreased. 【Conclusion】 Genistein can upregulate the proliferation and G1-S transition of ovarian cancer OVCAR-5 cells. The discrepancy may be caused by diverged experimental conditions and/or different ER expression patterns of cell lines. The findings may provide basic information for in-depth analysis of the role(s) and mechanisms by which genistein confers its effect on ovarian cancer cells.