Objective:To evaluate the effect of genistein(Gen) on the meiotic maturation of mouse oocytes. Methods:Mice were treated with different concentrations of Gen by intraperitoneal injection,and the oocyte production,germinal vesicle breakdown (GVBD),the extruding of the first polar body(PB1),in vitro fertilization(IVF) of mouse oocytes and embryonic development were observed. Murine immature oocytes were cultured in the media containing different concentrations of Gen. The rates of GVBD and the extruding of PB1 of mouse oocytes were detected after culture in vitro for 16 h and 24 h,respectively. Results:Administration of various doses of Gen significantly increased the weight of uterine and the number of ovulations(except high-dose group),prevented GVBD and the extruding of PB1 of mouse oocytes in vitro(except Gen-0.5 group). At concentration of 50.0 mg/kg,the capacity of fertilization of mature oocytes following in vitro fertilization(IVF) and embryo developmental capacity were decreased. Gen inhibited GVBD and the extruding of PB1 of immature mice oocytes in a dose-dependent manner after culture in vitro. Conclusion:Gen can reversibly inhibit the maturation of murine immature oocytes. At high concentration,Gen affected the process of the meiotic maturation,decreased the capacity of fertilization in vitro,suggesting that excessive intake of Gen by women at childbearing age may lead to reduced fertility,or even cause sterility or infertility.