The administration of anti-tuberculosis drugs to prevent the occurrence of tuberculosis in people already infected with the bacillus is called “drug prophylaxis. In China, the number of people infected with TB bacilli has reached 45%, so it is inappropriate to widely use drug prophylaxis, but it is necessary to give drug prophylaxis to special groups or key targets in order to reduce the occurrence of TB disease. The targets of drug prophylaxis are as follows: 1. Human immunodeficiency virus (HIV) infected patients. 2. young children and adolescents with close contact with newly diagnosed infectious TB patients who are tuberculin-positive. 3. Children under 5 years of age who have not received BCG vaccination with a positive tuberculin test. 4, tuberculin positive test of the following people: diabetic patients, silicosis patients, long-term use of adrenal corticosteroid hormone therapy, people receiving immunosuppressive therapy. 5.People who have inactive tuberculosis lesions on X-ray chest film and have not received anti-tuberculosis treatment, and those who receive chest radiation therapy. 6.People who have strong positive junction factor test.