Abstract: Objective: Detect carcinoembryonic antigen mRNA (CEA mRNA) and cytokeratin-19 (CK-19mRNA) in nucleated cells in peripheral blood from breast cancer. To establish an early diagnostic method for breast cancer micrometastasis in peripheral blood. Methods: Peripheral blood samples in breast cancer patients (test group,n=65) and benign tumour in breast patients (control group, n= 37) were taken. Then, separated nucleated cells and extracted total RNA, CEA mRNA and CK-19mR-NA was detected by nested reverse transcription polymerase chain reaction(nested RT-PCR) technique. Results: Samples were diagnosed CEAmRNA positive when 131 bp band is appeared in nested RT-PCR end-product, CK-19mRNA is460bp as well. The positive rates of CEAmRNA and CK-19mRNA is, respectively 407 (26/65) and 36.927(24/65) in test group. None benign tumor in breast patients express CEAmRNA and CK-19mRNA. The difference between the two groups was statistically significant (P<0.001). Conclusion: RT-PCR can be diagnosed in breast cancer micrometastasis, with relatively high sensitivity.