Recurrent aphthous ulcer, also known as recurrent aphthous stomatitis, recurrent oral ulcer, and recurrent mouth sore, is one of the most prevalent diseases of the oral mucosa. The disease can be occasionally caused by the common cold, indigestion, nervousness, depression, etc. It occurs on the lips, cheeks, and tongue edge, and can appear on any part of the mucosa. It is more frequent in women and can occur throughout the year. The disease is periodic, recurrent and self-limiting. Modern medicine believes that recurrent aphthous ulcers are first and foremost very closely related to immunity. Some patients show immunodeficiency, while others show autoimmune reaction. Secondly, there is a relationship with heredity. In clinical practice, the development of recurrent Aphthous ulcer has a clear tendency to run in families, and if one or more parents suffer from recurrent Aphthous ulcer, their children are more prone to the disease than the general population. In addition, the onset of recurrent aphthous ulcers is associated with a number of diseases or symptoms, such as digestive system diseases: gastric ulcer, duodenal ulcer, chronic or prolonged hepatitis, colitis, etc., in addition to partial eating, indigestion, fever, lack of sleep, excessive fatigue, stressful work, changes in the menstrual cycle, etc. With one or more factors active, the immunity of the body is reduced, resulting in frequent attacks of recurrent aphthous ulcers. To a large extent, mouth ulcers are related to personal physical quality, try to avoid triggering factors, can reduce the incidence. 1, pay attention to oral hygiene, avoid damage to the oral mucosa, avoid spicy food and local stimulation. 2, keep a relaxed mood, optimistic and cheerful. 3.Ensure sufficient sleep time and avoid excessive fatigue. 4.Pay attention to regularity of life and balanced nutrition, and develop certain bowel habits to prevent constipation. 5.According to the results of identification, taking herbal medicine appropriately can improve immunity and reduce or avoid the recurrence of mouth sores.