With rapid economic and social development in China, the number of migrant children 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 and Changzhou in Jiangsu province, this paper analyzed the current situation of migrant children in participating in medical insurance and its influencing factors through the establishment of Logistic model. The results showed that rate of the migrant children’s participation in medical insurance in these four cities of southern part of Jiangsu was relatively high. However, there were 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.