In order to reveal immunization status of children in migrating families and its related risk factors, a study was conducted in Beijing, Inner Mongolia and Fujian from August to November, 1996. Results showed that the overall coverage with BCG, OPV, DPT and MV was 34.26% (95% CI: 29.75%-38.94%). Many factors influenced the immunization status of floating children which mainly consisted of a) regular searching for new coming floating children conducted by EPI staff, b) awareness of parents on the number of the total EPI-targeted vaccines, c) home as the place that the child was born, d) the length did the child's mother stay at the place, e) how well did the parents comply to the vaccination and f) The type of hospital was chosen when seeing a doctor.