Abstract: Circulating tumor cells（CTCs） are increasingly attracted the interest of the people as an entry point to study the process of lung cancer metastasis. The “seed-soil” hypothesis of the nineteenth century on tumor metastasis has predicted the existence of CTCs. But it was only in recent years， a reliable， reproducible experimental methods for the detection and analysis of CTCs has been established. Currently， CellSearch assay has been widely used in clinical and has been certified by the FDA. CTCs counts can be used to guide the prognosis of patients with metastatic tumors， reflect the efficacy of anticancer drugs， and can monitor tumor recurrence. Analysis of CTCs molecular and genetic characteristics may be regarded as a noninvasive “liquid-based biopsy”，and it can reflect the molecular biology and genetics characteristics of the primary tumor tissue. In this review， we will discuss the biological characteristics of CTCs， its role in the process of tumor metastasis， currently the most commonly used detection method and the clinical value in lung cancer.