Occult syphilis, also known as latent syphilis, is a condition in which the patient has been infected with the syphilis spirochete, but the syphilis is in a lifelong latent state in the patient’s body, or the syphilis is only active at stage 2 or 3, which is manifested by a positive serological reaction, but there are basically no symptoms in the whole body, so it is also called latent syphilis. Latent syphilis is mainly due to the strong immunity of the body or insufficient dose of medication or incomplete treatment, resulting in the syphilis spirochete being only temporarily suppressed. Usually within 2 years of infection with syphilis spirochetes is early stage latent syphilis, which is infectious and can transmit the virus to others through sexual contact, blood transmission and mother-to-child transmission; while the course of the disease is more than 2 years is called late stage latent syphilis, the virus is less infectious or non-infectious state. The symptoms of latent syphilis usually do not include hard chancre and syphilis rash, but there are still syphilis spirochetes in the body. If the disease is not treated, when the resistance decreases, it may turn into dominant syphilis at any time and symptoms such as skin damage may appear. Therefore, once the infection of syphilis spirochetes is found, regardless of whether it is dominant or recessive, regular antiviral treatment must be carried out as early as possible to avoid missing the best treatment period. The treatment of recessive syphilis is the same as that of dominant syphilis, usually penicillin is preferred, and the treatment is carried out in sufficient quantity and duration.