Soil in open-pit coal mine spoil heaps is severely degraded by heavy machinery, disrupting structure, microbial communities, and the seed bank, which hinders plant recolonization. Arbuscular mycorrhizal (AM) fungi can enhance host plant growth and soil aggregate stability, mainly via extraradical hyphae and glomalin-related soil proteins, but their role in soil reconfiguration in mine dumps remains unclear. This study investigated the effects of AM fungal inoculation on soil microbial community structure and aggregate stability in Amorpha fruticosa cultivated on a four-year-old open-pit dump. The results indicated that AM fungi increased microbial richness, altered community composition, and notably enhanced bacterial diversity. AM fungal inoculation significantly boosted mycelium density, glomalin-related soil protein levels, and soil organic matter in the rhizosphere, leading to improved soil aggregate stability. Furthermore, this improvement was strongly correlated with mycelial density, glomalin-related soil proteins, and soil organic matter content. AM fungi indirectly influenced soil aggregate stability by shaping bacterial and fungal community diversity. These findings indicate that AM fungal inoculation drives soil aggregate development during early ecological restoration, accelerating aggregate formation, improving stability, and fostering microbial community recovery. This approach represents a promising strategy for rehabilitating arid and semiarid open-pit coal mine dumps.