Abstract: Twenty genistein derivatives with various basic side chains were synthesized and their structures were confirmed by IR,ESI-MS and ¹H NMR.Among these compounds,sixteen compounds have not been reported in the literatures.The effect of the target compounds on estrogen receptor levels of human breast cancer MCF-7 cells was evaluated in vitro in order to study the potency in selective modulation of estrogen receptor.The results indicated that compounds 4a , 4b , 4d , 4e and 4f showed quite potent inhibition on MCF-7 cells proliferation with inhibitive rates of more than 40% at 48 h and 72 h (P<0.01).Compound 9d could significantly induce MCF-7 cells proliferation with a growth rate of more than 15% at 48 h (P<0.05).