[Background] Microorganisms in grassland soils are important for ecosystem functioning and stability maintaining. To discover the profile of microbes along the soil vertical depths is essential for our understanding about microbial contributions in grassland ecosystems. [Objective] To comprehensively investigate the vertical patterns of total prokaryotic quantity, diversity and interaction networks in 0?80 cm soil profiles. [Methods] Based on the quantitative PCR and high-throughput sequencing on 16S rRNA gene in a typical agropasture grassland, Inner Mongolia, the total microbial quantity and diversity were cautiously measured. Besides, the molecular ecological network approach (MENA) was used to explore the changes of microbial species interactions. [Results] The quantity and diversity of prokaryotes decreased with depths, as well as the variations of community. Along the soil vertical depths, the close association among microbes would gradually become sparse and the network structures become simpler. In addition, Acidobacteria was one of top abundant phyla, and network analysis revealed that some species in Acidobacteria were the keystone taxa in this grassland ecosystem. These species might play an important role in maintaining the stability of soil ecological functions. [Conclusion] The quantity, diversity and interactions of prokaryotes showed highly consistent with vertical patterns. The quantity and diversity of prokaryotes is negatively correlated with the soil depth, and the variation of community structure will gradually expand at deep soils. Meanwhile the interactions among species in molecular network are decreasingly weakened. These results provide important insights into the dynamic change of microbial community, and are valuable for the ecological protection of grasslands in typical agropasture area.