Abstract: A multi-level scientific assessment of the effectiveness and impact of the policy of "defining the scales based on water" (that is "defining the scales of city, land, population, and production based on water resources") since its implementation is urgently needed. Based on summaries previous understandings and insights of the policy, the present study defines the underlying concepts and interprets its connotations, such as embodying harmonious coexistence, reflecting coordinated development, emphasizing policy implementation effectiveness, and highlighting the constraint of water supply capacity. The requirements and significance of conducting a multi-level evaluation of "defining the scales based on water" are analyzed. Based on the theory of harmonious coexistence, a multi-level evaluation framework was constructed, consisting of four layers: the human-water harmony layer, ecological coordination layer, water-use coordination layer, and suitable water balance layer. The contents of the different layers are described, and methods used for evaluation are presented, together with a case study performed in the Yiluo River Basin as a demonstration of applications. The paper also analyzes the prospects of multi-level evaluation in the planning of regional water resource management, the dynamic management and optimization of policy implementation, comprehensive monitoring and feedback of the effectiveness of implementation, and the long-term vision for high-quality development in the water sector. The findings of the study provide a reference for further research on the evaluation of "defining the scales based on water" as well as practical applications.