Given the steady progress of water saving work in China, and based on the basic law of natural social dual water cycle, the process and influencing factors of water use in various industries in the Beijing-Tianjin-Hebei region are analyzed, and the ultimate water-saving potential of stock water is calculated from two aspects such as water-saving and resource-saving. The results show that: the water saving potential and resource water saving potential of the Beijing-Tianjin-H ebei region are 1.144 bilion m3 and 636 milion m3, respectively, accounting for 5.4% and 3.0% of the total regional water consumption, with limited water-saving potential; according to the analysis of different industries, the water-saving amount and resource water saving amount of agriculture accounted for 51.0% and 59.3% of the total water-saving amount, respectively, agriculture is still the focus of regional water-saving; judging from research results, the calculation method of ultimate water-saving potential proposed can scientifically and accurately calculate the water-saving potential of regional or basin stock users, calculate and clarify the wa ter-saving target, and provide a reference for regional water resources management.