Objective：To understand the infection status and risk factors of syphilis among male drug addicts in a compulsory isolation detoxification center in Jiangsu Province. Methods：A cross-sectional survey was conducted among male drug addicts in a compulsory isolation detoxification center in Jiangsu Province from June to August 2018. The antibodies were detected by the syphilis particle agglutination test，and the basic information，drug abuse and sexual behavior were investigated using a questionnaire. Results：Among 790 people，133 cases of syphilis antibody were found to be positive. The syphilis infection rate was 16.8%. The average age of syphilis group（P < 0.001）and the average age of starting drug use（P=0.002）were higher than those of non-syphilis group. There was a difference in sexual partner between the two groups（P=0.044）；multivariate analysis showed that the average age of syphilis group（P < 0.001）and the average age of starting drug use（P=0.002）were higher than those of non-syphilis group. There was a difference in sexual partner between the two groups（P=0.044）；multivariate analysis showed that longer years of drug use（OR=1.04，95% CI：1.00~1.07）and temporary sexual partners（OR=1.90，95%CI：1.18~3.05）were risk factors for syphilis infection in this population. Conclusion：The syphilis infection rate is high in this population. It is associated with longer years of drug use and unsafe sexual behavior.