Over the last decade, the intensive and rapid retail internationalization has attracted wide attention across the social sciences. In particular, the local supply network impacts from retail transnational corporations (TNCs) purchasing activities have been discussed extensively by academic scholars, especially in terms of the host economies of Latin America. However, it is surprising that little similar research has been conducted in the world's biggest retailing market - China. Thus this paper adopts the global production networks (GPN) approach to explore these local supply network transformations in the Chinese market, and also identifies the mechanisms of upgrading process. The GPN framework refers to networks of firms and institutions, which pinpoints where value is created, enhanced and then captured throughout supply networks, highlights the dynamics of power within these webs of production, and reveals how retail TNCs make their attempt at embedding themselves in local markets. With the extensive interview-based fieldwork undertaken in Shanghai, China between 2014 and 2015 on two specific local supply networks, i.e., branded fresh milk and own branded edible oil, the paper examines the five ongoing shifts of the procurement activities adopted by retail TNCs in the host market. They are centralization of procurement, upgrading logistical systems, adoption of the specialized/dedicated wholesalers, private-standards enforcement and the development of private labels. The analysis demonstrates significant variations in both retailer management practices and strategic responses by suppliers between the two products. It reveals the dynamic power relations among retail TNCs, suppliers, wholesalers and logistics providers. In addition, a considerable restructuring and reconfiguration process has taken place in the local distribution, wholesale and agricultural production sectors, due to the increasing power exercised by retail TNCs. Finally, the paper calls for an in-depth study on the retailer power and its impacts based on the nuanced and dynamic approach, in an aim at better understanding the complexity and unevenness of supply network restructuring in emerging markets.