Syphilis serologic tests are divided into specific antibody tests and non-specific antibody tests, and only non-specific antibodies may turn negative after treatment. However, after the three injections, syphilis does not turn negative immediately, and it takes some time to turn negative, and the exact time varies from person to person. Syphilis is a sexually transmitted disease caused by syphilis spirochete infection. The higher the titer of non-specific syphilis serologic antibody, the more active the syphilis spirochete is. Penicillin is generally preferred for the treatment of syphilis, and the course of treatment is usually 3 injections once a week. After this course of treatment, most of the syphilis spirochetes in the body will be killed, but the titer of non-specific syphilis serologic antibody in the blood serum will not turn negative immediately. Therefore, it is generally recommended that the disease should be rechecked every three months, and with active treatment, the titer of syphilis antibody may turn negative only after a period of time, but not immediately.