Soil invertebrate biomass accounts for less than 10% of the total soil biomass, but it is characterized by abundant species, and diverse feeding behavior and life strategies, which can result in complex interactions among soil faunal groups and soil microbes. Soil fauna contribute primarily to ecosystem functioning through trophic and/or non-trophic effects. Soil protozoa, the most abundant faunal group with the highest turnover rate among soil fauna, equivalent to or even higher than that of soil bacteria, contribute to carbon and nitrogen mineralization via their own metabolic processes. In contrast, other soil faunal groups have much less impact on carbon and nitrogen mineralization, as compared to soil microbes. Most micro- and/or meso-faunal groups can regulate soil microbial processes directly by feeding on detritus and microbes, and indirectly affect soil carbon and nitrogen processes. In addition, predators such as spiders and ground beetles can affect soil ecosystems via the trophic cascade effects of predators. However, macrofauna such as earthworms and termites may regulate soil microbes, and thus alter soil carbon and nitrogen processes considerably by non-trophic effects. The diverse feeding strategies of soil fauna and the complex non-trophic relationships establish multi-dimensional soil food webs, and these pose enormous challenges to the studies of soil faunal function. Here, we outline briefly the diversity and ecosystem functioning of soil fauna, and highlight some frontiers and hot issues to inspire in-depth understanding of interactions between the diversity and function of soil fauna.