The notion of ethnic structure of society per se have been first singled out as the 'charger' of concepts of national and ethnic structures of society only at the end of the 1990's. The task of theoretical clarification of this problem is complicated by the unsettled state of concept-category apparatus, namely by identification of concepts of ethnic structure and ethnic composition of society, interpretation of nation as an ethnic phenomenon etc. The ethnic structure of society is one of the types (substructures) of its social structure. Consequently, the reasonable solution of society ethnic structuring questions is to be carried out on methodological principles of social structuring in general. The author uses as a basis Anthony Giddens' definition which assumes the social structure of society as a gnosiological construct. Meanwhile, the author emphsizes, that this structure is not merely a product of consciousness, but is the phenomenon based on relations between elements of empirically fixed ontological reality, that is social structure of a society. Therefore the relevant determination of the social structure notion presumes representation of its pluralistic essence and the distinction between social structure and composition of society. On these principles, the analysis of ethnic structure of a society is to be deepened up to the level of its concrete substructures, including ethnic one. Hereof, one can select its mere components brought up to tasks of political nation building.