Livestock grazing, the main type of management activity in grasslands drives the structure and function of these ecosystems. However, the responses of soil microbial biomass and community composition to grazing remain poorly understood, compared with plants, nutrients and soil properties. We conducted a meta-analysis of independent grazing intensity (low grazing intensity, intermediate grazing intensity and high grazing intensity) experiments, including 69 studies with 934 paired observations, in steppe ecosystems of China and evaluated their effects on soil microbial biomass and community composition. Our results revealed that high grazing intensity consistently reduces total microbial biomass, the biomass of bacteria, fungi, actinomycetes, gram-positive bacteria and gram-negative bacteria by 33%, 31%, 53%, 14%, 19% and 36%, respectively, whereas low grazing intensity has limited effect on these microbial variables. High grazing intensity strongly reduced the numbers of bacteria, fungi and actinomycetes by 92%, 65%, 30%, respectively, but low grazing intensity had limited effects on them. The responses of fungal numbers to grazing intensity were positively correlated with those of plant aboveground biomass. Meanwhile, the response of bacterial numbers was positively correlated to that of soil bulk density. Our findings indicate that aboveground plant biomass and soil bulk density might be the underlying drivers that change the numbers of fungi and bacteria to grazing intensities in China. Our findings highlight the negative effect of high grazing intensity on soil microbial biomass and numbers in natural grasslands.