A negative syphilis titer is not contagious to others. Syphilis serologic examination includes two categories of specific and non-specific antibodies, specific antibody test TPPA, non-specific antibody TRUST, the so-called syphilis titer mainly depends on the titer of the non-specific antibody TRUST, which can reflect the degree of syphilis spirochete in the patient’s body, the higher the titer the more contagious, and can also be used to evaluate the effectiveness of syphilis treatment. Generally speaking, after active treatment, the serum TRUST titer of syphilis patients can become negative, and the patients are no longer infectious. However, in this case, the syphilis-specific antibody TPPA is still positive, which is a sign of previous infection. However, it must be noted that the infection of syphilis to detect syphilis antibodies, there is a certain incubation period, the occurrence of high-risk sexual behavior within one month, syphilis serology may have false negative situation, this case of syphilis patients are infectious. In short, after adequate treatment of syphilis titer negative, this time is no longer contagious, but still need regular review.