1. Biodiversity and ecosystem multifunctionality are currently hot topics in ecological research. However, little is known about the role of multitrophic diversity in regulating various ecosystem functions, which limits our ability to predict the impact of biodiversity loss on human well–being and ecosystem multifunctionality. 2. In this study, multitrophic diversity was divided into three categories: plant, animal, and microbial communities (i.e., plant diversity, rodent diversity, bacterial and fungal diversity). Also, 15 ecosystem functions were divided into four categories–water conservation, soil fertility, nutrient cycling and transformation, and community production–to evaluate the significance of biotic and abiotic variables in maintaining ecosystem multifunctionality. 3. Results indicated that species diversity at multiple trophic levels had a greater positive impact on ecosystem multifunctionality than species diversity at a single trophic level. Notably, the specific nature of this relationship depended on the niche breadths of plants, indicating that plants were key indicators linking above and below ground trophic levels. Abiotic factors such as altitude and pH directly acted on ecosystem multifunctionality and could explain changes in ecosystem functions. 4. Overall, our study offers valuable insights into the critical role of multitrophic species diversity in preserving ecosystem multifunctionality within alpine grassland communities, as well as strong support for the importance of biodiversity protection.