Abstract: Objective：To detect CEA expression in peripheral blood of non-small lung cancer(NSCLC) patients and discuss the possibility of indicating NSCLC micrometastases by it. Methods：The expression of CEA mRNA was analyzed by RT-PCR in 48 NSCLC in peripheral blood,compared with 15 patients with benign lung disease(BLD) and 10 healthy volunteers. Results ：The positive expression rate of CEA mRNA was significantly higher in NSCLC than in those of BLD and healthy volunteers(P<0.01).The expression rate of CEA mRNA was 27.8%,83.3%,61.5%,100% in peripheral blood with non-small cell lung cancer of TNM stageⅠ~Ⅳ respectively.The positive expression of CEA was closely related with the clinical staging and lymph node metastasis(P<0.05),but not related to pathological type and tumor cell differentiation(P>0.05). Conclusion ：Expressions of CEA mRNA in peripheral blood can be used as a valuable biomarker for diagnosis of micrometastasis in patients with NSCLC.