IL-6 is a cytokine that plays an important role in response to injury or infection and is a promising biomarker for predicting poor prognosis and therapeutic targets in non-small cell lung cancer (NSCLC). This article reviews the biochemical mechanism, function and genotype of IL-6, and summarizes the diagnostic and prognostic value of IL-6 level. Anti-IL-6 therapy does not affect the effect of immunocheckpoint inhibitors (ICIs), but enhances its anticancer function, which may be the treatment option for immune-related adverse events (irAEs) in the future. Therefore, IL-6 may be a therapeutic target for the treatment of NSCLC.