Oral mucosal cells grow faster and are similar to tumor cells. Therefore, chemotherapy drugs can directly damage the oral mucosal epithelium and inhibit the growth of mucosal epithelium. At the same time, chemotherapy has a suppressive effect on the immune system of the body, which can easily lead to oral mucosal inflammation. Patients may show symptoms such as oral mucosal congestion, edema, ulceration, difficulty in eating and swallowing. The main drugs that cause oral mucositis are methotrexate, cytarabine, etc. Prevention of oral mucosal inflammation should be the main focus. Pay attention to oral hygiene throughout the chemotherapy process, rinse your mouth before and after eating, do not wear dentures, drink more water, eat a highly nutritious liquid or semi-liquid diet, avoid foods that are irritating to the oral mucosa, such as overheated and spicy, acidic foods, etc. Avoid foods that can easily damage the oral mucosa, such as fish and shrimp. Gargle with gentamicin gargle solution (gentamicin 240,000 units plus 500ml saline) or compound borax solution (dobei gargle solution) 3 times a day. If mouth ulcers have occurred, gargle with chlorhexidine, gentamicin gargle or compound borax solution every 1-2 hours. If the mouth ulcer is more serious and the pain is more intense, 2% lidocaine solution can be applied locally to relieve pain. Because of the low resistance of the body of patients with hematological diseases, it is easy to combine mycobacterial infection on the basis of oral ulcer, which is manifested as scattered white curd-like dots on the surface of mucous membrane, and then 2%-4% sodium bicarbonate gargle (baking soda water) and hydrogen peroxide gargle (hydrogen peroxide) can be given alternately. If the disease develops to a serious infection, the patient appears fever and other systemic symptoms, it is necessary to make smear in the mucosal inflammation as soon as possible, and take the oral cavity, pharynx and blood specimens for bacterial culture and drug sensitivity test to determine what kind of pathogenic bacteria infection, and then give the corresponding treatment, apply sensitive antibiotics as soon as possible to control the disease. In addition, the following are recommended: 1. Before starting chemotherapy, visit your dentist for a dental examination, such as cleaning your teeth and dealing with any problems in your mouth, including molars, abscesses, gum disease, or lack of dentures. 2. After meals, brush your teeth lightly with a soft-bristled toothbrush. If your gums are too sensitive, a non-irritating or soda-based toothpaste is more appropriate, or just wipe with a wet cotton pad. 3, avoid using commercially available mouthwash that generally contains more salt or alcohol ingredients, so as not to irritate too much and cause painful mouth ulcers. If you have ulcers in your mouth, ask your physician if you can be given some ointment to apply on the ulcers to reduce the pain. 4.Eat more cool foods and avoid hot foods to avoid irritating the ulcers. 5.Choose soft foods, such as ice cream, dairy products, soft fruits (such as bananas, apple puree, etc.), mashed potatoes, boiled cereals, boiled or scrambled eggs, macaroni, rice, soft pasta, etc. Juicer can be used to break up the cooked food to facilitate consumption. 6.Avoid acidic and irritating food to avoid irritating the wound and causing pain. 7.Soak dry and hard food in water or thick soup to make it softer before eating.