Background <p>Soil microbes are key regulators of ecosystem services, but how their diversity, network complexity, and stability interact to sustain ecosystem service multifunctionality (ESMF) remains unclear. We conducted an extensive field survey along a 1500 km transect in Inner Mongolia, establishing 101 sampling sites that encompassed three distinct steppe types: meadow steppe (MS), typical steppe (TS), and desert steppe (DS). We assessed the influence of steppe type on soil microbial attributes, as well as the role of bacterial and fungal diversity, network complexity, and stability in maintaining ESMF.</p> Results <p>Bacterial network complexity (BNC), fungal diversity (FD), and fungal network complexity (FNC) were all strongly influenced by steppe type (MS &gt; TS &gt; DS) and declined significantly with increasing aridity. In contrast, bacterial diversity (BD), bacterial network stability (BNS), and fungal network stability (FNS) were only weakly affected by steppe type. In Inner Mongolian steppe, BNC, FNC, FD, and BNS all exhibited significant positive associations with ESMF, with explanatory powers (<i>R</i>²) of 0.63, 0.17, 0.09, and 0.06, respectively. Even after controlling for other ESMF drivers, such as climate and soil factors, BNC remained the most effective predictor. Furthermore, microbial diversity indirectly regulated ESMF through its influence on microbial network complexity.</p> Conclusions <p>Our results indicate that soil microbial network complexity, particularly bacterial network complexity, plays a critical role in sustaining ecosystem service multifunctionality. These findings provide crucial insights into how soil microbial communities drive and regulate ecosystem services in steppe systems.</p>