Abstract: Carbon, nitrogen and water cycles in terrestrial ecosystem are three critical subjects in global change science. The coupling modes of these cycles and their biological regulation mechanisms had been frontier issues in global change ecology. At present, lack of knowledge on the processes of carbon-nitrogen-water coupling cycles and the regulation mechanisms had limited assessment of terrestrial carbon sink enhancement and emission reduction. This had become a major problem in predicting the effects of global change on the productivity and carbon sequestration of ecosystems. Based on synthetic analysis of terrestrial ecosystem carbon, nitrogen and water cycles, this paper expounded biogeography mechanisms that limited spatial patterns of coupling cycles. It also discussed biological and physio-ecological mechanisms that limited the coupling cycles and the key biophysical and biochemical processes. The main processes and biological regulation mechanisms of carbon-nitrogen-water coupling cycles discussed included: 1) biological processes of plant leaf canopy/root canopy and its regulation mechanism on carbon-nitrogen-water coupling cycles and the interactions among them; 2) soil microbial functional group network and its effects on carbon, nitrogen and water cycles; 3) spatial and temporal variations in carbon, nitrogen and water fluxes in terrestrial ecosystem along with the theory and practice of ecosystem stoichiometry. Finally, the paper briefly introduced the strategic schemes and main contents of the key programs of National Natural Science Foundation of China-Biological Control Mechanisms of the Coupling Cycles of Carbon, Nitrogen, and Water in Forest Ecosystem. This had the potential to promote the theory and technique of developing related fields.