Objective To summarize the clinical features and analyze the serologic test results of latent syphilis. Methods The clinical data of 601 patients with latent syphilis who were treated in the sexually transmitted disease centre of Peking Union Medical College Hospital between January 2001 and November 2007 were retrospectively analyzed. Results Of the 601 cases of latent syphilis,there were 174 cases of early latent syphilis(EL),170 cases of late latent syphilis(LL),and 257 cases of unknown latent syphilis. Male to female ratio was 0.74:1（256 males and 345 females,respectively). Patients aged 20-39 years accounted for the largest proportion. Non-marital sexual intercourse was the main route of infection. Forty-six patients (7.65%) were co-infected with other sexually transmitted diseases. A total of 251 cases of latent syphilis (41.76%) were confirmed when the patients were receiving tests for other sexually transmitted diseases or suspected sexually transmitted diseases. Of the 601 patients with EL,LL and unknown latency,the proportion of serum rapid plasma reagin(RPR) titers higher than or equal to 8 were 72.99% (127/174),52.94% (90/170),and 60.31%(155/257),respectively. Compared with the early syphilis,serological negative conversion rate was significantly lower after treatment for l2 months in the early latent syphilis patients (P=0.044). Conclusion Education and awareness raising on syphilis should be strengthened to lower the prevalence of latent syphilis.