Abstract: Objective To investigate AIDS-related knowledge and practice and infection with HIV/syphilis among sex workers in Daxing district, Beijing. Methods Anonymous questionnaires were designed to survey the sex workers in entertainment places with blood sample collected for HIV and syphilis test. Results Most of the 105 subjects were unmarried with low education levels. They had certain knowledge on the prevention and transmission routes of HIV, though only a small group of them answered correctly to whether mosquitoes disseminated HIV (36.19%). Low condom use rate was found in the subjects. One subject was detected positive anti-HIV antibody, the positive rate being 0.95%, and three detected positive syphilis RPR (2.86%). Conclusion The infection rate of HIV /syphilis among sex workers was low in Daxing district. It is necessary to strengthen relevant health education, prevention and intervention in this population.