Abstract This paper introduces the species diversity and the functions of soil nematodes. Nematodes are ubiquitous with diverse feeding behaviors and life strategies. The diversity of feeding behaviors and some intrinsic properties result in the complex biotic interaction between soil nematodes and other soil biota, which greatly affects the ecosystem functions. However, the research on the species diversity of soil nematodes and their ecosystem functions is still inadequate. To understand the role of soil nematodes in the ecosystem requires: (1) the combination of laboratory microcosm study and field mesocosm experiments; and (2) the combination of biodiversity survey and functional analysis of different groups.