Abstract: In response to the severe challenges faced by China, including frequent extreme climate events and water pollution incidents, and severe over-exploitation of groundwater in northern regions, the authors in this research systematically carried out the delineation of the country's major aquifers and key national groundwater reserve zones. A methodological framework was innovatively proposed and established for selecting and evaluating national major aquifers and key groundwater reserve zones, based on nearly 70 years of hydrogeological survey data, and the groundwater system theory. Forty-six national major aquifers and thirty-eight key national groundwater reserve zones were delineated. The study systematically elaborated on the advantageous conditions, potential sources for storage replenishment, safety considerations, and groundwater reserve capacities of each key reserve zone. including details such as current groundwater storage, potential replenishment volume for reserves, and emergency extractable volume. For the first time, the distinct characteristics and differences among Quaternary porous water aquifers, carbonate karst water aquifers, bedrock fissure water aquifers, as well as key reserve zones in North China, Northwest China, Northeast China, and the South (South China and East China) were demonstrated. And strategies and recommendations for the construction, protection, and rational development of national groundwater reserve zones were proposed. This research could provide scientific basis for establishing the national emergency groundwater supply security system and hold significant strategic importance for enhancing China's resilience against extreme events and ensuring water supply security for key economic regions such as the Beijing-Tianjin-Hebei area and the Yangtze River Delta.