Abstract: Based on mutualistic symbiosis of rice and duck,plus the technique of no-tillage,a new no-tillage rice-duck complex system was formed.In order to provide a scientific and theoretic foundation for ecological assessment,experiments were carried out to determine effects of the new system on CH₄ emission and its mechanism.Results show that the no-tillage rice-duck complex system combined the benefits of no-tillage and raising ducks in rice field.It decreased CH₄ emission greatly as a result of increased dissolved oxygen by duck activities and changes in soil physical properties and redox conditions related to adoption of no-tillage,which helped CH₄ oxidation.