Abstract: Objective To describe the situation and to analyze the risk factors of human immunodeficiency virus(HIV),hepatitis c virus(HCV),and syphilis infection among men who have sex with men(MSM) in Nanning city.Methods Using respondent driven sampling(RDS) method,2 296 MSM were recruited and the information about HIV/AIDS prevention-related knowledge,behavior characteristics in the MSM were collected with a face-to-face questionnaire survey.Serological tests for HIV,HCV and syphilis infection were conducted simultaneously.Univariate and multivariate logistic regression model were adopted to analyze risk factors of HIV infection.Results The average age of the MSM was 30.61?7.68 years and 65.3% of them were Han ethnic.The most common way for finding sexual partners was internet contact(63.6%).Awareness rate of HIV/AIDS prevention-related knowledge was 95.4%.In the previous half year,86.3% of the MSM had homosexual and 75.2% of them reported condom use when having anal sex.In the previous half year,13.1% of the MSM had heterosexual behavior and 40.7% of the MSM reported condom use when having sex behavior with female.During the period of 2009-2010,HIV,HCV,and syphilis infection rates in the MSM was 3.2%,0.3% and 10.1%,respectively.The results of multivariate analysis showed that education level,gender of the first sexual partner and having anal sexual behavior in the previous half year were risk factors of HIV infection.Conclusion The MSM in Nanning city have active sexual activity but lack awareness of safe sex and high rates of HIV and syphilis infection.Effective interventions should be implemented to reduce the risk of HIV infection among the MSM.