The role that biodiversity plays in ecosystem functioning has attracted much attention during the last decade because of concern over the currently unprecedented rate of biodiversity loss. However, most studies of diversity——ecosystem functioning relationships have been performed in single trophic level, mostly plant communities, although recent studies have shown that consumers diversity have a profound effect on the structure and functioning of ecosystems. This paper reviews recent developments on the effect of consumer diversity on population density, species diversity, and production, of adjacent and non-adjacent trophic levels, and also suggests several research perspectives. In general, consumer diversity, of either herbivore or predator, tends to increase nutrient and energy use efficiency, and the productivity of the trophic level, which may result from sampling effect, and/or complementary between species, as found for the relationship between plant species diversity and primary productivity. Herbivores may decrease or increase plant species diversity, biomass, and primary production, depending on ecosystem productivity, herbivore identities, and environmental gradient. Predators usually have an indirect, positive effect on the plant diversity and primary production via a direct, negative effect on the herbivores, but the positive effect can be weakened and even the effect direction can be changed when intraguild predators occupy a large proportion of the predator density. In future, large-scale experiments, both of spatial and temporal, should be conducted to explore the effect of complex trophic interaction in real food webs on ecosystem properties, especially of terrestrial ecosystems. We propose that allometric growth law and ecological stoichiometry theory may be applied to study the trophic cascading effect of consumer diversity in order to improve the understanding of the relationship between biodiversity and ecosystem functioning. In addition, the effects of global warming and growing transgenic plants on consumer diversity and ecosystem functioning should be studied in recent future.