Abstract: Objective To understand the AIDS related knowledge, attitude and practice (KAP) and HIV infection status among floating population in Ningbo and provide scientific evidence for developing prevention and control strategy. Methods Through stratified cluster sampling, a face to face questionnaire survey was conducted in 4 floating population groups, the blood samples were collected from the participants to detect HIV and syphilis antibodies, and the data were analyzed by using software SPSS 16.0. Results The awareness rate of AIDS related knowledge was 65.9% according to 4002 valid questionnaires, there were significant differences among different floating population groups (2=59.355, P0.001). The factors influencing the awareness rate included gender (OR=1.172, 95% CI: 1.019-1.248), age (OR=0.656, 95% CI: 0.550-0.783), marital status (OR=1.440, 95% CI: 1.209-1.715), education level (OR=1.598, 95% CI: 1.374-1.859) and HIV counseling (OR=2.164, 95% CI: 1.537-3.048). Totally 29.7% of participants in the survey said they wouldnt discriminate against HIV/AIDS patients, 20.5% of them used condom in the latest sex with permanent sexual partner, 62.2% used condom in the latest commercial sex and 42.9% used condom in the latest homosexual activity. The infection rates of HIV and syphilis were 0.15% and 0.72% respectively. Conclusion Low education, poor awareness of AIDS related knowledge, discrimination against HIV/AIDS patients, high risk sexual behavior characterized by poor condom use are risk factors among floating population to make them vulnerable for HIV infection. It is important to strengthen health education and behavior intervention in this population.