Mitral stenosis is a common clinical rheumatic heart valve disease, and many patients feel that mitral stenosis is very difficult to prevent, especially at the beginning of the disease, the symptoms of mitral stenosis are very inconspicuous, so many people can not do effective prevention. Here we will see how to prevent mitral stenosis. 1, primary prevention: refers to the prevention of the first attack of rheumatic fever, the key is the early diagnosis and treatment of nail chain tonsillitis, all fever, sore throat or discomfort, headache, abdominal pain, pharyngeal congestion and tonsil secretions should be made before treatment swab culture of the throat to determine the presence of nail chain growth, if positive, antibiotic treatment should be started immediately. Penicillin should be the preferred drug for all patients except those with penicillin allergy for the following reasons: (1) All strains of Streptococcus aureus are equally sensitive to penicillin. (2) After more than 40 years of application, the average inhibitory and bactericidal concentrations of penicillin against this bacterium have not changed and remain at about 0.005 μg/ml. (3) No signs of resistance to penicillin were observed. (4) No other antibiotic has so far exceeded the activity and clinical effect of penicillin G against streptococcal infection. 2. Secondary prevention: (prevention of rheumatic fever recurrence) Continuous antibiotic treatment is required for those with a clear history of rheumatic fever or existing rheumatic heart disease to prevent rheumatic fever recurrence. (1) duration of prevention: depends on the risk of recurrence, in general, those who have frequent upper respiratory tract infections, those who live in crowded conditions, those with poor medical conditions and those with a history of multiple attacks have a high risk of recurrence, and the duration of preventive medication should be long; conversely, it can be appropriately shortened. In contrast, patients who have not had rheumatic heart disease have a low risk of cardiac involvement in the event of recurrence, and antibiotic prophylaxis can be discontinued after a few years. (2) prevention program: intramuscular injection of benzathine penicillin G: commonly used program is a long-acting penicillin preparation benzathine penicillin G 1.2 million U, intramuscular injection, once every 4 weeks, in countries and regions with a high incidence of acute RF, and high-risk patients, better intramuscular injection every 3 weeks. Oral antibiotics: Patients with a low risk of RF recurrence, such as those who have reached late adolescence or young adulthood or who have not had a recurrence of rheumatic fever for at least 5 years, may switch to oral antibiotic prophylaxis.