Abstract： Objective To examine the prevalence of and risk factors for syphilis among men who have sex with men (MSM) in 16 cities/districts, 6 provinces in China. Methods Based on a previous survey on the entertainment place and population size of MSM, a cross-sectional study was conducted in 2007 using non-probability sampling method among MSM in 16 cities/districts in China.Information about the demography,risk behavior and syphilis infection was collected through questionnaires from MSM. Univariate and multivariate stepwise logistic regression model was constructed to evaluate independent factors associated with syphilis. Results A total of 4211 participants were recruited. The mean age of these participants was 28 years. Among them, 66.7% were self identified as homosexual, 72.5% were unmarried, and 76.4% had an education beyond senior middle school; in the past 6 months, 8.7% had sexual contact with more than 10 male sex partners, 5.6% had ever paid for male sex service, 11.3% had provided commercial sex service to males, and 18.9% had sexual contact with females, while condom was consistently used in only 36.3% of male-to-male anal sexual behavior. Syphilis was diagnosed in 10.6% of these participants. The risk factors independently associated with syphilis included being older than 25 years (adjusted OR = 1.7; 95% CI:1.3-2.0), local residency (adjusted OR = 1.3; 95% CI: 1.0-1.7), being recruited from a bar or a park (adjusted OR = 1.3; 95% CI: 1.1-1.7), having ever paid for a male sex service(adjusted OR = 1.5; 95% CI: 1.0-2.1),inconsistent condom use during male-to-male anal sexual behavior(adjusted OR = 1.2; 95% CI: 1.0-1.5 ), self reported sexually transmitted infection history (adjusted OR = 1.3; 95% CI: 1.0-1.7). Conclusions There is a high prevalence of syphilis in MSM in the 16 Chinese cities where male-to-male commercial sex service and unsafe sexual behavior are common. Further efforts are urgently needed to scale-up the prevention of and treatment program for syphilis among MSM, which should include syphilis and HIV screening as well as education on the use of condom.