Abstract: Objective To understand HIV and syphilis infection and high-risk behaviors among men who have sex with men(MSM) in Shenzhen,and to provide basis for effective intervention in the population.Methods By recruiting MSM volunteers,a self-administered anonymous questionnaire and blood test were conducted among 450 MSM with sexual behavior with men in the previous 6 months using snow balling sampling.Results The average number of male partners of the MSM was 5.02±1.23,and 18.67% of the MSM had sex with female.Among the MSM,5.35% bought sex from male and 7.26% sold sex to male.Totally 46.21% of the MSM could persist in using condom when having anal sex with male.There was a significant difference in the frequency of condom use among four different kinds of sex partners among the MSM (χ²=34.1484,P< 0.0001).The infection rate of HIV and syphilis was 5.56% and 18.44%,respectively.Multivariate logistic regression analyses show ed that low er monthly income(odds ratioOR=0.707,P=0.0039) was risk factor of HIV infection,and older age(OR=1.713,P=0.0073) and low er monthly income(OR=0.843,P=0.0419) were risk factors of siphilis infection.Conclusion The frequency of condom use among the MSM was low,and most of the MSM had multiple sex partners and heterosexuality.The infection rate of HIV and siphilis was very high among the MSM in Shenzhen.Intervention efforts must be strengthened to control the epidemic of HIV and sexually transmitted disease.