Definition: Serofixation, also known as seroresistance, refers to the non-syphilis spirochete serologic test (e.g., VDRL test) in syphilis patients after anti-syphilis treatment, which does not change to negative within a certain period of time. One somewhat controversial issue is that some people advocate that 6 months after anti-syphilis treatment for early syphilis and 1 year after treatment for late syphilis do not change to negative is diagnosed as serum fixation; others advocate that 1 year after anti-syphilis treatment for early syphilis and 1.5 years after treatment for late syphilis do not change to negative as serum fixation. Reason: Early serum fixation: related to insufficient amount of treatment or irregular treatment, relapse, reinfection or having neurosyphilis. Therefore, when early serum fixation is found, it should be carefully examined, especially the cerebrospinal fluid, and if necessary, it is necessary to give double the dose of retreatment. Late syphilis serum fixation: it is related to the early or late start of treatment. In general, the serum fixation of cutaneous mucosal syphilis is only 50%-60%, while paralytic dementia also shows serum fixation after adequate treatment. After adequate treatment of late syphilis serofixation physicians do not have to worry too much, because its prognosis and infectiousness is not significantly different from those without serofixation (but must be carefully examined, except for the presence of neurological, cardiac or other visceral syphilis.