Abstract: Objective To observe the effect of effective component of Chinese herb Psoralea corylifolia, Psoralen, on MCF-7 cell line and to identify the changes of gene expression profile by using cDNA microarray. Methods Antitumor test of Psoralen on MFC-7 cells was done in vitro. The total RNA was isolated from two groups: Psoralen-treated and DMSO-treated.They were hybridized with HUMAN 22K oligo chip to screen the gene expression profile and analyze the gene expression difference between the two groups. Results The 1053 genes among the total 22k(4.78％)showed expression difference in the cDNA chip: 657 genes(56.7%,Ratio<0.5)were down-regulated and 456 gene(43.3%,ratio>2.0)were up-regulated, which was involved in many scopes such as apoptosis,regulation of cell cycle, regulation of nucleic acid transcription, translation factor activity, nucleotidyl transferase activity, regulation of vasoconstriction and so on. Conclusion The antitumor molecular mechanism of Psoralen may be regulating many genes such as apoptosis gene, gene of cell cycle and nucleic acid transcription．