As an important component of soil ecosystems, soil fauna play an important role in the process of soil element cycling, transformation and migration. Soil fauna is regarded as litter decomposition “micro-muller”, and through the body “special converter”, it can accelerate the formation of soil humus. Based on the soil fauna on the earth's surface litter decomposition, this paper summarized the influential factors of soil fauna on litter decomposition, transformation and migration of soil elements and formation of humus in soils. Soil fauna combined with microbes accelerated the decomposition of soil organic matter, and transformation of soil humus by stimulating soil enzyme activities. The purposes of this paper were to broaden the soil fauna ecological functions and to expand the theory of soil humus formation. The contents of the paper would provide important references for protecting soil biodiversity, improving soil fertility, and safeguarding grain security.