Abstract: Objective: To detect the micrometastases in peripheral blood of patients with breast cancer using MUC1 and CK7 as a gene marker and to discuss the clinical value. Methods: MUC1 andCK7 mRNA expression of the nucleated cells in circulating peripheral blood were analyzed using re-verse transcriptase polymererase chain reaction (RT- PCR). Results: a) 15 normal peripheral blood samples were detected and, it turned out that no MUC1 and CK7 mRNA expression was false- positive;breast cancer cells MCF-7 were mixed with normal peripheral blood nucleated cells at the concentra-tions of 1:10 ⁵, 1:10 ⁶, and no MUC1 and CK7 mRNA expression was detected to be false-negative. b) Of the 35 patients with breast cancer,11 (30.3%) were positive for MUC1 mRNA expression and 12 (35%)were positive for CK7 mRNA expression of the nucleated cells in circulating peripheral blood. c) Of the 35 patiens, 4 were positive for both MUC1 and CK7 expression, 7 were positive for only MUC1, 8 were positive for only CK7 and the patients positive for both two markers were crossed but not overlaped.Conclusion: Using RT-PCR to detect micrometastases in peripheral blood of the patients with breast cancer, with MUC1 and CK7 as a gene markers, can be used as a prognostic indicator and the multi-marker detection were better compared to single marker.