Objective To investigate the toxicity of genistein (GEN) on oocyte maturation in mice. Methods In vivo test, mice were randomly divided into 4 groups and administrated with genistein (0,0.5,5.0 and 50.0 mg/kg BW)for 7 days. After superovulation, the ovulated oocytes picked up from oviduct ampulla were counted, and the estradiol (E₂), follicle stimulating hormone (FSH) and luteinizing hormone (LH) in serum were detected. During in vitro test, cumulus-oocyte complex (COCs) and denuded oocytes (DOs) were collected from super-ovulated mice and cultured by different concentrations of GEN to evaluate the influence of GEN on oocyte meiotic maturation. Results The number of superovulated oocytes in animals was significantly decreased by GEN treatment, while sex hormone remained unchanged. GEN produced an evident impact on the meiotic process of in vitro cultured COCs but DOs. Conclusion Our result confirmed the influence of GEN on oocyte maturation of mice, with its potential mechanism in ovary.