Based on the China Migrants Dynamic Survey from 2010 to 2014 and the Chinese General Social Survey, this paper takes the 12-year compulsory education system reform implemented by various cities in China as a quasinatural experiment, and uses the Differences-in-Differences method to find that the implementation of the 12-year compulsory education policy covering the floating population has significantly promoted the urban integration degree of the equivalent group. With the increase of the number of migrant children and school-age children, the degree increases. The theoretical analysis of this paper holds that the basic decision-making unit of population flow into cities is the family. Parents' consideration of their children's access to compulsory education is the key factor for them to integrate into the city and become citizens. This study provides a reference for all regions to formulate effective policies to accelerating the urban integration and citizenization of floating population.