Diarrhea after the first chemotherapy for rectal cancer can generally be maintained with water-electrolyte balance and drug treatment. 1. Maintaining water-electrolyte balance: oral rehydration salts can be taken, in addition, if the diarrhea is serious, electrolytes should be checked, and intravenous fluids can be given. 2. Drug treatment: during chemotherapy, there will be more or less diarrhea, of course, there are more serious cases, for example, diarrhea will be heavier when applying irinotecan chemotherapy, but in most cases, chemotherapy does not need to be stopped, and loperamide hydrochloride capsules should be applied for treatment. Rectal cancer patients with diarrhea after chemotherapy should eat some easy-to-digest light liquid food, such as egg custard, rice soup can be. In addition, spicy and stimulating, raw and cold diet should not be eaten. Rectal cancer patients with big side effects during chemotherapy should closely observe the patient’s gastrointestinal reaction, take measures immediately if diarrhea occurs, and make sure to let the patient drink more boiled water so as to avoid dehydration caused by diarrhea. If patients have serious diarrhea during chemotherapy, they should seek medical treatment in time.