Lung cancer is the most frequent cancer and the leading cause of cancer death all around the world. Anti-programmed cell death 1 (PD-1)/programmed cell death-ligand 1 (PD-L1) therapies have significantly improved the outcomes of non-small cell lung cancer (NSCLC) patients in recent years. However, the objective response rate in non-screened patients is only about 20%. It is very important to screen out the potential patients suitable for immunotherapy. Immunohistochemical staining of tumor tissue biopsies with PD-L1 antibodies can predict the therapeutic response to immunotherapy to some extent, but it still has some limitations. Recently some clinical studies have shown that PD-L1 expression in circulating tumor cells (CTC-PD-L1) is a potential independent biomarker and may provide important information for immunotherapy in NSCLC. This article will review technology for CTC-PD-L1 detection and the predictive value of CTC-PD-L1 for immunotherapy in NSCLC and review the latest clinical research progress.