The objectives of this study are to observe the theoretical background of brand extension, to compare & analyze the cases of brand extension in Domestic and abroad based on the existing studies to present the characteristics of brand extension strategies, and to contribute to the establishment of marketing strategies of brand portfolio for the globalization of national brands. As for the methods of research, literature review and case study were combined. As a result of the case analysis, fashion business possessing a lot of brands have powerful competitiveness when they consider the brands as one unit and manage them with definition and insight to produce mutual synergy. Given that brand environment is being complicated and diversified with market segmentation, brand extension, various product groups, numbers of competitors, and complex distribution structure, the hierarchical structure of brand may have even more significance as a strategy.