<p>This is the first study to examine how earthworm abundance influences the composition, interactions of co-occurrence network, and diversity of soil bacterial and fungal community. In a controlled greenhouse experiment involving the addition of endo-anecic earthworms (<i>Metaphire guillelmi</i> L.) at different abundances, the bacterial and fungal communities were investigated under planting wheat potting greenhouse experiment for 24 weeks, employing Illumina sequencing and high-throughput quantitative PCR techniques. We found that earthworm addition, particularly at higher abundances, increased total carbon (TC), soil organic carbon (SOC) and nitrate nitrogen (NO₃⁻-N), as well as bacterial and fungal species richness. High-abundance treatments enhaned the Chao index for both the bacterial and fungal communities, and the Shannon diversity index of the fungal community. Principal Component Analysis (PCA) and Non-metric Multidimensional Scaling (NMDS) indicated that earthworm abundance significantly altered microbial community composition. Redundancy Analysis (RDA) confirmed that NO₃⁻-N were the most influential factors shaping microbial structure, which were affected by earthworm feeding and burrowing activity. At low earthworm abundances, microbial species tended to exclude each other, whereas higher abundances promoted positive species interactions. Additionally, earthworm presence strengthened the co-occurrence network between bacteria and fungi. These results emphasize earthworms as prominent ecological engineers, whose density not only increases soil microbial richness, promotes beneficial microbial associations, and reorganizes soil microbial networks but also enhances nutrient cycling and soil fertility, highlighting new insights into the ecological function of earthworms and their potential uses in sustainable soil management.</p>