Abstract: Objective: To explore the value on detection of CEA mRNA and telomerase activity (TA) in blood for diagnosing distant metastasis of the digestive system cancers. Methods: CEA mRNA and TA in blood were detected by reverse transcriptase-nested primers- polymerase chain reaction (RT-NP-PCR) and telomeroc repeat amplification protocol-hybridism-enzyme- linked immunosorbent assay (RTAP-Hyb-ELISA) in 67 cases with digestive system cancer and 44 patients of digestive system diseases without cancer. There were 35 cases with distant metastasis and 32 without metastasis in the cancer patients. Results: The positive rates of CEA mRNA and TA in the cancer patients were far higher than in the patients without cancer (P<0.001). The positive rates of CEA mRNA and TA in the cancer patients with distant metastasis were far higher than in the cancer patients without metastasis (P<0.001). Conclusions: The detection of CEA mRNA and TA in blood is helpful in predicting distant metastasis of digestive system cancer.