To comprehend the young migrants' sexual behavior and contraceptive status, and to provide the scientific basis for the health education regarding sex and reproduction for the young migrants in cities.An anonymous self-designed structured questionnaire was used to survey 4 389 young migrants in Beijing, Guangzhou and Ji'nan.In the study, 33.4%(1 453/4 354) of the migrant adolescents reported had sexual activity, with the unmarried sex rate of 27.5%(1 066/3 880), and the males accounting for 37.8%(579/1 533) and the females 20.7%(487/2 347); contraception was 44.8%(642/1 432); condoms were the preferred contraceptive measures for floating adolescents; but 31.1%(322/1 034) of the unmarried persons reported experienced pregnancy, and 29.7%(307/1 034) of the unmarried people reported had a history of abortion. Education backgrounds (OR=1.555), marital status (OR=0.432), sex partner number (OR=0.683), knowledge of venereal disease prevention (OR=1.758) were the influence factors.Higher sexual and lower birth control utilization rates have triggered young migrants' reproductive health problems. We should promote the floating people' s reproductive health education and make better choices for effective contraceptive measures.