Water system is constantly changing under the influences of climate changes and human activities so that the development and utilization of water resources should be adapted to these changes rather than conform to a fixed control threshold or certain constraints. Therefore, studying the adaptive utilization and management of water resources is of great significance. In this paper, the principle and mode of adaptive utilization of water resources (AUWR) is expounded based on the analysis of water system and its relationship with environmental changes. Based on the understanding of the mechanism of AUWR under environmental changes, the theory of adaptive utilization of water resources (AUWR theory) is put forward, a framework system of the theory is constructed, and its basic concepts and key contents are expounded. Based on the analysis of modern water management practices in China, this paper elaborates on the underlying AUWR theory, and the existing problems in modern water management practices in China as well as the possible solutions to these problems using the AUWR theory. The study shows that the AUWR theory can provide significant guidance on the rational development, comprehensive utilization, and scientific management of water resources, as well as lay the theoretical foundation for the research and practice of water resources utilization under environmental changes.