Abstract: Immune checkpoint inhibitors (ICIS) are widely used in the treatment of a variety of malignant tumors, but the over activation of the immune system induced by ICIS will also lead to T cells attacking their own antigens, and cause a series of immune related adverse events (IRAEs) in clinic. Immune checkpoint inhibitor associated pneumonia (CIP) is a rare but potentially fatal immune related adverse reaction that occurs at any time of tumor immunotherapy. Clinicians should understand the mechanism and characteristics of CIP, and identify and deal with it correctly as soon as possible. This paper reviewed the epidemiology, biological mechanism, clinical characteristics, diagnosis and treatment of CIP.