Beijing resident alien population of 802.7 million，of which a large proportion of migrant workers，in 2013.In the background that low-end industrial will be relocated and population inflows will be controlled in Beijing，what about right and interest of migrant workers？In this paper，through the social insurance investigation of migrant workers，analysis how to balance between population control and the interests of migrant workers agis. The survey shows：social insurance of migrant workers is not satisfactory. The research analyze its causes from the perspective of the institutional structure，and proposed to promote the principles of migrant workers social insurance system building.