Diarrhea after chemotherapy for lung cancer is mainly considered as infection factor and drug side effect. 1. Infectious factors, during chemotherapy for lung cancer patients, there will be bone marrow inhibition such as low white blood cell and platelet, which will cause immunity destruction, and gastrointestinal infections such as unhygienic diet will cause diarrhea and abdominal pain, etc. It is necessary to use antibiotics for anti-infectious treatment, and commonly used drugs include levofloxacin, cefoperazone and ceftazidime. 2. Drug side effects, chemotherapy drugs with toxic side effects will cause stimulation of the gastrointestinal mucosa, causing diarrhea, watery stool problems, is a normal reaction, generally no special treatment, treatment can be improved naturally; if the situation is serious, you need to use montmorillonite powder, tannins, subcang tablets, etc. for treatment.