The treatment of patients with advanced lung cancer has been revolutionized with the advent of immunotherapy. However, not all patients can benefit equally from immunotherapy. In recent years, the relationship between intestinal flora and the efficacy of immunotherapy has gradually attracted scholars' attention. During the treatment of immune checkpoint inhibitors, the use of antibiotics, proton pump inhibitors and other drugs will affect the patient's intestinal flora, thus affecting the efficacy of immune checkpoint inhibitors, leading to poor prognosis of patients. This review will discuss that antibiotics and proton pump inhibitors reduce the efficacy of immunotherapy by affecting the diversity of intestinal flora, in order to facilitate the rational use of related drugs in clinical practice and improve the patient's outcomes.