The cycles of carbon, nitrogen and water in terrestrial ecosystems are the three main substance cycles concerned by ecosystem ecology and global change science for a long time. They represent the energy flow, nutrient and water cycles of global, regional and typical ecosystems. However, the cycles of carbon, nitrogen and water in natural ecosystems are closely linked and coupled, and are controlled and regulated by multiple biological, physical, and chemical processes. In this paper, based on a comprehensive analysis of the theoretical and practical significances of carbon-nitrogen-water coupling cycles in terrestrial ecosystems, we firstly explored the key processes of carbon-nitrogen-water coupling cycles in terrestrial ecosystems, and raised the basic scientific issues in this research field. Second, we mainly analyzed the biophysical processes of carbon, nitrogen and water from vegetation-atmospheric, soil-atmospheric and root-soil interfaces,and clarified the biological and chemical processes of carbon, nitrogen and water cycles in typical ecosystems. Third, we pointed out the ecosystem ecological mechanisms constraining the carbon-nitrogen-water coupling cycles in terrestrial ecosystems, as well as the biogeographical mechanisms constraining the spatial pattern of carbon-nitrogen-water coupling relationships. Finally, on the basis of existing scientific studies, we built up the logical framework for researching the carbon-nitrogen-water coupling cycles in terrestrial ecosystems, and discussed the main technical approaches and methods for studying it.