Objective: To detect the expression of CEA mRNA in patients with non-small cell lung cancer (NSCLC) and to investigate it’s significance. Methods: The blood samples were taken from peripheral veins of 70 patients with NSCLC and 18 patients with benign diseases at 3 intervals during the surgery. The transcription of carcinoembryonic antigen messenger ribonucleic acid (CEA mRNA) was assayed by means of nested reverse transcriptase polymerase chain reaction (RT-PCR) and micro-fluid chip. Results: The CEA mRNA positive rates at each of the 3 time spots were as follows: 50% at beginning of the surgery (group 1), 62.8% in the samples collected when ligating the pulmonary vein (group 2) and 57.1% in samples collected 1 h after ligation (group 3). A significant difference was found between groups 1 and 2 (χ2 = 7.114, P < 0.05). Con-clusion: Cancer cell dissemination during surgery is demonstrated indirectly in our study, when to ligate the pulmonary vein (earlier or later) may affect the quantity of tumor cells spread into the circulation. Methods: The blood samples were taken from peripheral veins of 70 patients with NSCLC and 18 patients with benign diseases at 3 intervals during the surgery. The transcription of carcinoembryonic antigen messenger ribonucleic acid (CEA mRNA) was assayed by means of nested reverse transcriptase polymerase chain reaction (RT-PCR) and micro-fluid chip. Results: The CEA mRNA positive rates at each of the 50% at beginning of the surgery (group 1), 62.8% in the samples collected when ligating the pulmonary vein (group 2) and 57.1% in samples collected 1 h after ligation (group 3). A Significant difference was found between groups 1 and 2 (χ2 = 7.114, P <0.05). Con-clusion: surgery cell was indirectly in our study, when to ligate the pulmonary vein (earlier or later) may affect the quan tity of tumor cells spread into the circulation