Neutrophil-to-lymphocyte ratio (NLR) is defined as the number of neutrophils divided by the number of lymphocytes and is a sign of a general immune response to different stress stimuli. Neutrophils and lymphocytes are considered to play an important role in the development of tumors. Neutrophils have anti-tumor effects but also promote the occurrence and development of tumors. On the contrary, lymphocytes are the most prominent anti-tumor cells (especially CD8+T lymphocytes). NLR considers both the roles of neutrophils and lymphocytes, reflecting the changes in bone marrow production that occurs in chronic inflammation in lung cancer patients. NLR is an easy-to-measure and repeatable marker, which provides simple and inexpensive access of evaluation for lung cancer-related inflammation. The dynamic evolution of the balance state of NLR throughout the whole diagnosis and treatment of lung cancer provides insights for lung cancer patients, especially for predicting the treatment failure of non-small cell lung cancer in the early stage, tumor progression and prognosis, and planning future follow-up as well as treatment.