Abstract: Litter decomposition was a key ecological process of nutrient cycling in the forest ecosystem, which played an important role in the terrestrial ecosystem and was an important part of the global carbon budget. Litter decomposition rate controlled the nutrient cycling and energy flow, and then regulated the carbon emission in the atmosphere, the composition of soil organic matters and the nutrient availability. The chemical properties of litters, environmental climate, root system and microbial community composition regulated the decomposition rate of litter. By systematically summarizing the basic theory of litter decomposition, the role and regulation mechanism of root system during the root and litter decomposition, and the research progress on the non-additive effects of the decomposition of mixed litters, the complex regulation mechanism involved by multiple factors in the process of litter decomposition was discussed, and the future research direction was prospected.