Abstract: Spatial equilibrium is an important guide for water conservancy development in the new era, and it is the basic requirement for water conservancy work to be carried out. How to realize spatial equilibrium control of water resources is an important content and challenge of water conservancy development. Based on the author′s previous research on the theoretical method and applied research framework of water resource spatial equilibrium, this paper expounds the theoretical requirements and basic principles of water resources spatial equilibrium to answer "Why should we implement spatial equilibrium of water resources?"; the theoretical framework and main content of water resources spatial equilibrium are introduced to answer "What is the theory of water resources spatial equilibrium?"; the application rules and quantification methods of the spatial equilibrium theory of water resources are put forward to answer "How to apply the theory of water resources spatial equilibrium?" The application rules include following three major rules, conforming to three principles, undertaking four tasks, and having three functions, which are the criterion for correctly applying the theory of spatial balance of water resources. The quantitative methods include quantification of spatial equilibrium criteria for water resources, calculation of spatial equilibrium degree of water resources, spatial equilibrium optimization model for water resources, spatial equilibrium planning for water resources, and early warning assessment and comprehensive regulation of water resources spatial equilibrium. It is believed that the theory of spatial equilibrium of water resources is an important support for guiding regional and basin water conservancy and even for integrated spatial equilibrium development. The study provides solutions and specific methods for perfecting the theory of water resources spatial equilibrium and implementing spatial equilibrium control.