Abstract: Objective To explore the effect of geniste in on cell growth and possible mechanism of estrogen dependent human breast cell MCF-7 at a low level of estrogen environment.Methods The proliferation effect of MCF-7 cell was analyzed by MTT.Flow cytometry and Annex in V/PI a ssay were used to analyze the cell cycle distribution and apoptosis.Indirect mimuno fluorescence a ssay was used to detect the expression of eestrog enregulated protein(presenilin 2,PS2).Results Compared with the control group,the cell prolife ration,DNA synthesis and the expression of PS2 prote in of MCF-7 cell were markedly enhanced by geniste in at the concentra tion of 5×10^-7~10^-5 mol/L.However,the effect of apoptosis inhibition was not obvious.Conclusion Genistein enhances cell proliferation,D NA synthesis and the expression of PS2 protein of human breast cancer cell MCF-7 at a low level of estrogen environment,which may demonstrate an estrogenic effect.