Anorexia nervosa is a mental disorder characterized by long-term unexplained anorexia and significant weight loss, which, if left untreated, can lead to severe malnutrition and extreme exhaustion and affect the physical and mental health and development of adolescents. The onset of the disease is above the age of 10 years, and it is more common in female adolescents. Due to long-term excessive dieting or refusal to eat, the disease causes severe weight loss, nutritional deficiency, metabolic and endocrine dysfunction, and can be life-threatening in severe cases. The first symptom of the disease is obvious anorexia, the daily food intake is reduced by more than 2/3 compared with before the onset of the disease, the patient loses weight, the weight loss is more than 20% of the original weight, in addition to anorexia, nausea, vomiting and persistent constipation are also seen. As a result of prolonged under-eating, patients may suffer from malnutrition and hypometabolic symptoms, such as cold body, cold fear, bradycardia, hypotension, and rough skin. Secondary amenorrhea may occur in girls who are already menstruating. Most of the cases can still support general indoor activities and can go to school and study. A few cases are depressed and unresponsive, and although they are extremely thin, they still do not think about eating and avoid treatment. Anorexia nervosa is mainly treated by a comprehensive approach. Psychotherapy: The aim is to make the patient understand the disease through interpretive psychotherapy, cognitive therapy, behavioral therapy, etc., and rebuild a healthy and mature psychological defense mechanism, and remove the bad family atmosphere that causes the disease through family psychotherapy, which is the key to cure the disease and prevent recurrence. Dietary management: Encourage the patient to eat less and more, take the initiative to eat, supplement nutritious food and vitamins, and tabulate the daily food intake, using each progress to strengthen the patient’s confidence. If the systemic nutritional status is extremely poor, intravenous or intragastric intubation of nutrient solution should be used for those who have difficulty in eating to correct malnutrition and water-electrolyte disorders. Medication: New antidepressants can be used first to improve the patient’s mood, to increase the patient’s appetite, to stop vomiting with sulpiride, etc., and to reduce the patient’s psychological resistance with anti-anxiety drugs. This disease is far from benign and is one of the few psychiatric diseases that can be fatal, so it is important to be highly alert and pay attention to it. The mortality rate reported abroad is 7% to 20%, and the cause of death is mainly due to severe metabolic disorders and physical failure, so that the infection cannot be controlled and fatal. So, how can we prevent the occurrence of the disease as much as possible? First of all, emotional prevention: the disease is more frequent in women, indicating that the instability of character during this period, vulnerable to external stimuli, or discord at home, conflicts between parents, or parental education is too harsh, too strong in family status and unexpected setbacks, etc., are prone to the disease, so it is vital to maintain mental optimism and open-mindedness. Second, the combination of work and rest, so that the combination of mental work and appropriate physical exercise, physical work, appropriate arrangements for recreational activities and rest, can prevent the hypothalamus function disorders caused by overwork. Thirdly, the education of correct human beauty, a few cases have stubborn prejudice and pathological psychology about eating and obesity, so that there is a strong fear of becoming fat and diet, to maintain the so-called physical “beauty”, so the education of correct health “beauty” is also indispensable. Therefore, the education of correct and healthy “beauty” is also indispensable.