Based on the significant demand for achieving healthy regional water balance, systematic exploration has been conducted around the threshold system of water balance and its application fields. The correlation between water balance theory methods, threshold systems, and application fields is clarified, and the implementation path of healthy regional water balance is analyzed. An architecture of the water balance threshold system with characterization indicators and indicator thresholds as the core is constructed. Starting from the perspectives of water budget balance, water supply-demand balance of economic society, water use balance between economic society and ecology, and harmonious balance of human-water relationship, characterization indicator systems are sorted out. The expression forms of indicator thresholds are defined with consideration of limits, ranges, and patterns, and the methods for determining the thresholds are introduced. Considering theme relevance, theoretical compliance, and method applicability, the application fields of regional water balance are analyzed. The research contents corresponding to the four major balances and the overall research ideas are presented. Four examples are selected for in-depth analysis:attribution analysis of water resource changes based on water budget balance, synergetic optimization of water-energy-food-ecology based on the water supply-demand balance of economic society, calculating the potential of water resource development and utilization based on the water use balance between economic society and ecology, and human-water relationship regulation based on the harmonious balance of human-water relationship. Keywords: regional water balance; threshold system; application field; human-water relationship; water cycle 〖FL