Abstract: By examining and comparing the specific logic of reference group selection and the effect of relative position of permanent migrants and floating population in Chinese metropolis, this paper reveals the mechanism of micro-perceptions of distributive justice from the perspective of social comparison theory. Three types of reference groups of homogeneous reference, origin reference and native reference are constructed for this study in order to answer the question of "to whom the reference is made". Also by using the contrast of satisfaction desirability and loss aversion, the study explores the psychological aspect of "how the comparison is made". To the former question, the finding indicates that in reporting distributive justice perception, hukou status is the institutional basis for reference dependence. Those holding metropolis hukou become the reference objects for permanent migrants, while floating migrants are more likely to treat all metropolis residents as one reference group. Origin reference groups are not selected by both permanent and floating migrants as a reference point even after elements like social network structures, migration years, migration intergeneration, and etc. are taken into consideration.To the question of "how comparison is made", the study finds that the relative position gap creates an asymmetric effect among both permanent and floating migrants. Migrants with superior positions tend to show some egalitarian sentiment while those with lesser positions display "loss aversion", whose sense of dissatisfaction is much stronger than the satisfaction felt by the former group. The comparative analysis of this study has practical implications for the management of migrant population in Chinese metropolis.

Key words: perceptions of distributive justice, reference groups, relative position, migrants in Chinese metropolis, permanent migrants, floating population