The theory and practice of sub-provincial central cities originated in Hubei Province and subsequently spread nationwide. Based on a review of the theoretical and practical backgrounds and the promotion process of provincial sub-central cities, as well as an analysis of their development motivations, functional characteristics, and policy support mechanisms, this paper proposes policy recommendations for the development and expansion of provincial sub-central cities. Specifically, it suggests seizing opportunities, optimizing the layout of provincial sub-central cities, increasing policy support, granting them greater economic and social management powers, improving infrastructure and service functions, building a modern industrial system, and leveraging sub-central cities as the leaders to construct urban agglomerations and metropolitan areas, thereby enhancing their radiation capabilities and promoting the modernization of provincial governance systems and governance capacities.