【Objective】 The investigation was carried out to better understand the factors influencing the coverage of national immunization program (NIP) vaccines in migrant children in Wenzhou, and to improve the immunization coverage of these vaccines. 【Method】 Population characteristics of 1 198 migrant children and their guardians, immunization situation of NIP vaccines, knowledge of the guardians on and their attitude towards preventive immunization, effectiveness of preventive immunization, were investigated in 15 towns from 3 counties in Wenzhou by using randomized sampling method. 【Results】 In the migrant children over one year old, who stayed in Wenzhou equal or more than 3 months, the coverage rates of BCG, OPV, DTP, MV, and HepB, were 86.8%, 84.9%, 81.5%, 82.1%, and 80.35%, respectively. Notably, the coverage rate of these five vaccines was only 66.4%. Multi-factors analysis revealed that the low coverage rate of five vaccines was mainly influenced by the staying time and birth place of migrant children, their family economy, having immunization card, cost of preventive immunization, their guardians' attitude towards to preventive immunization. 【Conclusion】 Vaccination rate was low in migrant children, many factors were influence it, and it should be taken targeted intervention to imporve immune status.