Effects of Daidzein or Genistein on the proliferation and antioxidation of mammary epithelial cells of dairy cow were investigated in vitro. 10 groups were assigned including blank control, estradiol (E2) group(10 ng/mL), different concentrations of Daidzein (1, 10, 100, 1 000 ng/mL) and Genistein (1, 10, 100, 1 000 ng/mL) groups. The MMT method was used to determine the proliferation effect of Genistein or Daidzein, and the results showed that Genistein at the concentration of 10 and 100 ng/mL, and Daidzein at the concentration of 100 and 1000 ng/mL significantly improved dairy cow mammary epithelial cell proliferation (P<0.05) , while significantly weaker than E2 group(P<0.05). In the antioxidation experiment, the T-SOD and GSH-PX activity, MDA and NO content of the mammary epithelial cells at the logarithmic growth phase treated with Daidzein or Genistein for 24 h were measured and the results showed that 100, 1000 ng/mL Daidzein, and 100, 1000 ng/ mL Genistein significantly increased the T-SOD activities and decreased MDA content (P<0.05).1 000 ng/ mL Daidzein and 100, 1 000 ng/mL Genistein significantly increased the GSH-PX activites (P<0.05). The results showed that proper levels of daidzein and genistein can improv the proliferation and antioxidation function of mammary epithelial cell of dairy cows.