Based on the balance concept, the definition of water use balance between economic society and ecology was put forward aiming at the competitive issue of water use between economic society and ecology, and its connotation and characteristics were interpreted. A framework for calculation rules of water use balance between economic society and ecology was constructed following four laws and six theories, taking six factors into account, and conforming to three criteria, and calculation ideas, including three steps of data processing, quantitative calculation, and result checking, were put forward. In addition, the calculation method and result representation form were introduced. Taking the representative year of 2019 in the Qin River Basin as an example, quantitative calculation of its water use balance between economic society and ecology was carried out. On the basis of solving the primary equilibrium point and the balance results under the rigid constraints of water use in economic society, water use in ecology, and comprehensive benefit, as well as comprehensive consideration of the six factors and the relationship between total amounts of water demand and water resources, the water use balance point between economic society and ecology in the Qin River Basin was determined, i.e., the ratio of water use of economic society and that of ecology was 0.71∶0.29. Keywords: water use balance between economic society and ecology; regional water balance; calculation rules; human-water relationship; Qin River Basin