Syphilis is one of the most common classical sexually transmitted diseases in clinical practice. Because of the popularization of medical knowledge and the excellent efficacy of penicillin on syphilis, most patients are no longer afraid of talking about syphilis, but they still do not know much about the phenomenon of “serum fixation” of syphilis, so I hope this article can answer some of your questions. The so-called syphilis “serum fixation” phenomenon, refers to a small number of syphilis patients in the regular anti-syphilis treatment, non-syphilis spirochete antibody titer down to a certain level (generally ≤ 1:8) that no longer fall, and long-term maintenance in the low titer (or even lifetime), that is, the serum fixation phenomenon. Syphilis “serum fixation” phenomenon occurs mainly because of the following reasons: 1, the anti-syphilis drug dose is not enough or treatment is not regular, the choice of drugs is not appropriate; 2, the syphilis stage, type and start of treatment time early or late (the risk of occurrence of late disease and failure to timely treatment is higher); 3, there has been a relapse or reinfection, the body still has 4, recessive neurosyphilis; 5, impaired cellular immune function; 6, combined with HIV infection The phenomenon of “serum fixation” does not need to panic, to the regular dermatological venereal disease department by a professional doctor according to the standard diagnosis and treatment can be. The current treatment of syphilis “serum fixation” is as follows: 1, if the drug dose is insufficient or treatment irregularities should be supplemented with a course of treatment; 2, a comprehensive physical examination, including neurological and cerebrospinal fluid examination, in order to early detection of asymptomatic neurosyphilis, cardiovascular syphilis. If necessary, HIV testing should be done. 3.Strict regular observation, including whole body physical examination and serum follow-up. If the titer tends to rise, retreatment should be given. If retreatment is given, the treatment regimen is: aqueous penicillin 4 million U, every 4 hours, intravenously for 14 days; followed by long-acting penicillin 2.4 million U, intramuscularly, once a week, for 3 times. According to the data, the RPR titer decreased by more than 2 dilutions in 48.6% after 3 months, 78.4% after 6 months, 94.6% after 9 months and 83.8% after 12 months of treatment. The efficacy is relatively satisfactory. Other alternative re-treatment regimens are: procaine penicillin 2.4 million U daily, intramuscularly for 15 days; or ceftriaxone 1~2g, intravenously or intramuscularly, once daily for 15 days.