Cancer patients with diarrhea seriously affect their quality of life and treatment effect and even life - threatening. Diarrhea can be caused by tumor itself but also by various treatments such as radiotherapy and chemotherapy targeted drugs immunotherapy intestinal infection drugs tumor surgery enteral nutrition and other factors. The clinical manifestations of tumor-associated diarrhea are mainly divided into the following three types gastrointestinal symptoms systemic intoxication symptoms and water electrolyte and acid-base balance disorders. Classifying these symptoms as " uncomplicated" or " complex" can help to determine the appropriate treatments. For patients with uncomplicated tumor - associated diarrhea of grade 1 or 2 and no other complications conservative treatments such as health education oral rehydration and antidiarrheal therapy is preferred. Complex tumor-associated diarrhea including grade 1 or 2 diarrhea with risk factors such as moderate to severe cramping ≥ grade 2 nausea and vomiting fever sepsis gastrointestinal bleeding etc. grade 3 or 4 diarrhea requires hospitalization and further evaluation of the condition and close monitoring of vital signs and can be actively treated with maintenance basic glucose and electrolyte infusion. A multidisciplinary team including gastroenterologists should conduct the assessment.