Gay men were supposed to be at high risk of HIV infections. The aim of this study is to determine the knowledge, attitudes and behaviors related to HIV/AIDS among gay men. A crosssectional survey was conducted and questionnaires were administered to 142 gay men in Shenzhen, China. Blood samples were detected. 114 respondents (80.28%) were valid return. The results showed: (a) Knowledge and attitudes: 77 respondents (67.5%) thought themselves unlikely to be infected with HIV; 48 men (37.2%) had no proper understanding of HIV infection routes; 32 men (28.1%) had no idea of the ‘window period’ process; 95 men (88.0%) thought it is necessary to use a condom when having sex with men. (b) Behaviors: 5 men (4.4%) respondents had a history of drug abuse; 52 men (45.61%) used a condom every time when having sex with men; only 21 men (18.7%) used a condom at first sex experience; 78 men (68.3%) reported anal intercourse; 32 men (28.1%) reported commercial sex; 32 men (28.1%) had multiple sex partners. (c) Blood samples detection: 2 HIV-positive cases (1.75%) and 14 syphilis cases (12.3%) were found. The study concludes that gay men were less aware of HIV/AIDS knowledge and had high-risk sexual behaviors. They were risk of suffering from sexually transmitted diseases.