Penicillin has been the drug of choice for the treatment of all stages of syphilis, but treatment failure has occurred. Anti-cardiolipin (aCL) titers in the rapid plasma reactin ring card test (RPR), venereal disease research laboratory test (VDRL), and toluidine red serum unheated test (TRUST) are often associated with disease activity. After the diagnosis of early syphilis, most patients can achieve clinical cure and serum cure with a 4-fold reduction at 3 months and an 8-fold reduction at 6 months after treatment, but in some patients, the aCL drops to a certain titer (usually ≥ 1:8) and stops dropping, remaining at a low titer for more than 3 months, or even remaining positive for life, called serum fixation. In a study of 465 patients treated for early syphilis, serum fixation was observed in 96 patients (21%) at 6 months after treatment; seroconversion at 6 months after treatment was associated with early stage of disease (87.0%, 85.8% and 62.1% for stage I, II and latent syphilis patients, respectively), baseline titers >1:32, young age of onset, few sexual partners, and the occurrence of the Gihay reaction at initial treatment. factors. The association of serofixation with co-infection with HIV or asymptomatic neurosyphilis has also been reported. Several domestic and foreign cellular immunology studies based on different subjects have shown that patients with syphilis serofixation have a severe Th1/Th2 immune imbalance and cellular immunosuppression, with impaired ability of the organism to completely clear spirochetes. Patients with latent syphilis are more likely to be clinically converted to serofixation, and this group of patients, although clinically healthy, has a different infection status and immune status in vivo. Serum fixation after syphilis treatment is not uncommon in clinical practice, and its pathogenesis is unclear. Whether serum fixation indicates a persistent infection or represents an infection-induced persistent autoimmune response in patients remains controversial as to whether and how patients with serum fixation need to be treated. Early findings suggest that high-dose penicillin treatment does not improve serum fixation. In fact, non-syphilis spirochete antigen tests in serofixated patients may remain positive for life. Patients who develop serum fixation do not need to be treated with penicillin several times, and further tests can be performed to clarify the cause of serum fixation: e.g. cerebrospinal fluid tests, immune function tests, etc. Regular follow-up, peace of mind and a healthy lifestyle.