Abstract: Objective : To identify evidence of pathogenesis of breast cancer by analyzing differential expression of the oncogene and antioncogene existing in breast cancer and normal breast tissues. Methods : The related human tumor genes containing 288 genes were chosen for preparation of the oligochips probe. mRNA was extracted respectively from the 16 breast cancer tissues and the corresponding normal breast tissues, and a cDNA probe was prepared through reverse -transcription and hybridized with the gene chip. A laser focused fluorescent scanner was used to scan the chip. The different gene expressions of computer software were thereafter automatically compared and analyzed between the two sample groups. Cy3/Cy5>3.5 meant significant up-regulation. Cy3/Cy5<0.25 meant significant down -regulation. Results : The comparison between the breast cancer tissues and their corresponding normal tissues showed that 84 genes had differential expression in the Chip. Among the differently expressed genes, there were 4 genes with significant down -regulation and 6 with significant up -regulation. Conclusion : Compared with normal breast tissues, the expressed genes do partially exist in breast cancer tissues. These genes of different expression are closely related with the occurrence and evolution of breast cancer.