Abstract: Objective To investigate the knowledge about AIDS and the ability and behavior of condom use among migrant populations in Beijing city.Methods Between May and June 2010,stratified multi-stage random cluster sampling was used to select 1 498 migrant persons aged 16-69 years from construction companies,restaurants,hotels,entertainment places,and pedlars' markets in Chaoyang district of Beijing city.Data were collected through a test for behavior of condom use and a self-designed questionnaire about demographic characteristics,AIDS-related knowledge and frequency of condom use.Results The AIDS awareness rate of the participants was 65.98%(987/1 496).Among the participants,72.03%(1 079/1 498)knew that the person who was infected with human immunodeficiency virus(HIV)could not be recognized from the appearance and 72.90%(1 092/1 498)knew that mosquito bites could not transmit HIV.The ratio of the participants having sexual intercourse was 85.65%(1 283/1 498),among whom only 191 used condom every time during sexual intercourse.Only 26.04%(390/1 498)of the participants could use condom correctly,and 39.32%(589/1 498)could properly clarify that the rolled-up ridge of the condom needed to be on the outside and holding correctly the bulb at the end of condom to make sure there was no air trapped inside.Logistic regression analyses showed that the influencing factors of condom use included age,education level,AIDS awareness,and the ability of condom use.Conclusion Migrant populations in Beijing city have a high risk to take unsafe sexual intercourse and more health interventions are needed to enhance the awareness of AIDS and the ability of condom use.