From a molecular level to an ecosystem scale,different coupling mechanisms take place during coupled carbonnitrogen-water (C-N-H2O) cycle,of which essential are water flux and related biogeochemical processes through physicochemical reactions associated with terrestrial and aquatic ecosystems.Meanwhile,regional coupled C-N-H2O cycle will subsequently impact regional gross primary productivity (GPP) and C and N exchanges during air-water interactions that occur downstream of watersheds.This study aimed to first synthetically analyze the regional dynamics of C,N and H2O cycles in ecosystems and determine their interactional relationships;second,to specify regional C-N-H2O coupled relationships of ecosystems and their theoretical ecological principles;third,to classify coupled regional response and adaptation of the C-N-H2O cycle to climatic and environmental changes under anthropogenic activities,providing a theoretical basis to fully understand and make adjustments to interactional C,N and H2O cycling relationships at different ecosystem scales and under associated coupling processes.