With China’s rapid economic and social development, the number of migrant is gradually increasing. To properly resolve problems of medical insurance of this ‘marginalized’ group is a key to constructing a more equitable social security system. Based on the research in Nanjing, Suzhou, Wuxi, Changzhou, Jiangsu province, this paper analyzes the current situation of migrant children in participating in medical insurance and its influencing factors through the establishment of Logistic model. The results show that rate of the migrant children’s participation in medical insurance in these four cities of southern part of Jiangsu is relatively high. However, there are still some problems in related policies. Health situation, education levels of parents, family per capita monthly income are main factors that affecting the migrant children’s participation of medical insurance.