Lung microbiome is defined as the specific microbiota of lung. Lung microbiome can make the lung in a state of chronic inflammation through direct destruction, activation of inflammatory cells and release of inflammatory factors, and then progress to lung cancer. There are significant differences in lung microbiome between lung cancer patients and healthy people. Some specific microbial flora can be used as a diagnostic marker of lung cancer. Specific microbial communities are related to the efficacy of immunotherapy, and microbial composition may be used as a marker of immune-related adverse events. There are both challenges and opportunities for research on the relationship between lung microbiome and lung cancer. This review will focus on the significance and value of lung microbiome in the occurrence, diagnosis and immunotherapy of lung cancer, in order to provide a reference for basic and clinical researchers in related fields.