From the functional sense, institutions import has made the spontaneoussocial stratification formalized and fixed, and labels the different stratum with clearidentifiable character, from which an obvious stratum hierarchy can be visible.This research takes stratification of the floating population after importing systemof resident permit in big cities as an example, and identifies another social stratifi-cation mechanism. As far as floating population concerns, the income gap amongdifferent stratum is not so significantly large; however, the social security, employ-ment, education chance and mobility upward vary largely across different sub-stra-tum. Re-stratification of stratum arises from some kind of interaction among insti-tutional factor, human capital, unit and social relations. Since the policy is not neu-tral, it seems unfair due to selective or discriminative character.