Plant and soil microbial communities jointly sustain ecosystem multifunctionality (EMF) in temperate grasslands, yet their relative contributions to EMF under grazing management remain poorly understood. We simultaneously investigated three temperate grasslands to assess the effects of grazing management, climate, edaphic properties, plant and microbial communities (diversity and community composition) on EMF (quantified by potential soil nitrogen (N) mineralization, arbuscular mycorrhizal fungal infection rate, phospholipid fatty acid, soil total carbon (C) and N, inorganic N, and plant biomass). Using random forest modeling, we identified important predictors, followed by structural equation modeling (SEM) to disentangle their relative roles. The results showed consistent declines in plant diversity and EMF with increasing grazing intensity, while soil bacterial and fungal diversity exhibited minimal responses. Heavy grazing management significantly reduced the abundance of perennial forbs and rhizome grasses, but increased that of annuals and legumes. Concurrently, we observed a significant decrease in copiotrophic Proteobacteria abundance accompanied by an increase in oligotrophic Gemmatimonadetes abundance. Random forest modeling identified grazing intensity, climate, soil properties, plant diversity and community composition, and bacterial community composition as important predictors of EMF. SEM revealed that plant diversity was the dominant biotic predictor of EMF, exceeding the influence of microbial communities across all grasslands. Notably, aridity indirectly influenced EMF through plant diversity rather than direct regulation. These findings demonstrate that plant diversity primarily maintains EMF under grazing pressure, highlighting the importance of biodiversity-focused management strategies in temperate grassland conservation.