Terrestrial ecosystem carbon cycle plays an important role in global carbon cycle because of its complexity and uncertainty.Study on terrestrial ecosystem carbon cycle relates to global climate change and potential ways or means to address.This paper is attempting to provide an overview of mechanism and research method of terrestrial ecosystem carbon cycle and a perspective of emphases and hotspots on the research of terrestrial ecosystem carbon cycle.We conclude that it is prospective to be researched in the application of science of complexity to terrestrial ecosystem carbon cycle.Terrestrial ecosystem is a complex adaptive system.The inner interaction of ecosystem is the main driving force for the self-organization,complexity and order in the ecosystem.This paper discusses mechanism and development of ecosystem complexity,by applying the principle and methods of complexity science which is a new approach for understanding ecological and evolutionary problems.