Generally speaking, there are 3 ways of transmission of syphilis, namely direct transmission, indirect transmission and fetus virus transmission. The vast majority are directly transmitted through unclean sexual intercourse, which statistically accounts for 95% to 98% of all patients. Because syphilis patients often have lesions on the skin and mucous membranes of the genital area, there are many penetrating spirochetes in the lesions or in the exudates on the surface of the lesions, and these lesions are painless and itchy, and do not impede sexual life. If a patient lacks medical knowledge, pays no attention to the lesions and continues to have sex, he or she will transmit syphilis to the other person. During sexual intercourse, the mutual friction of the genitals often causes microscopic damage to the skin and mucous membranes, and the patient's syphilis spirochetes can easily take advantage of the situation and invade a healthy person, with corresponding damage on his or her pubic area or genitals. Secondly, kissing or other similar sexual behaviors can also transmit syphilis, and the damage can occur on the lips, tongue, fingers, breasts and other parts of the mouth. Or direct contact with the patient's lesions, secretions and excretions can also cause infection.

Indirect infection refers to indirect contact with the patient's contaminated clothes, bedding, towels, razors, cigarettes, toys, medical equipment with syphilis spirochetes, as well as medical personnel to handle the patient inadvertently and be infected, but the chances of this infection is very small, and occasionally there is also a medical infection, the importation of syphilis patients to provide the blood can also occur after syphilis.

Another type of infection occurs when a woman with active syphilis becomes pregnant and is not thoroughly treated, so that the syphilis spirochetes in the blood pass through the bloodstream and invade the fetus through the placenta, infecting the fetus with syphilis in the mother's womb. This kind of delivery before the mother in the body of syphilis called fetal syphilis, is congenital syphilis, and the first two ways of transmission of syphilis called acquired syphilis, or known as acquired syphilis or self-acquired syphilis.