Black sputum after immunotherapy for lung adenocarcinoma is mostly considered to be caused by bronchial invasion, infection or adverse reaction of immunotherapy. 1. Invasion of bronchial tube: immunotherapy for lung adenocarcinoma is not 100% effective, and some patients will still experience aggravation of the disease in the course of treatment, and the bronchial tube is invaded, and the blood vessels rupture and bleed during coughing, which will become black when it stays in the bronchial tube for a long time. CT, MRI and other examinations should be carried out in time to determine the location of the lesion, and surgery, radiotherapy and other anti-cancer treatments should be taken. 2. Infection: Lung adenocarcinoma patients with low immunity are susceptible to bacterial infection during treatment, and black sputum may also occur, and they need to use penicillin G, procaine penicillin, ceftazidime, cefpirome and other antibiotic drugs to carry out anti-infection treatment in time. 3. Adverse reaction of immunotherapy. Lung inflammation caused by immunotherapy will also make spit black. It is suggested that patients with black sputum after immunotherapy for lung adenocarcinoma should go to the hospital in time to find out the cause of the disease.