<p>Addressing the challenges of carbon and nitrogen loss and low humification during livestock manure composting, this study employed cattle manure as the substrate for vermicomposting by <i>Eisenia fetida</i>. The effects of adding 4% biochar (VEB), struvite (VES), or shell powder (VEO) on earthworm growth, carbon and nitrogen transformation, and intestinal microbial community were investigated. Results demonstrated that compared to the control (VEK), both VEB and VES significantly enhanced the growth of <i>Eisenia fetida</i>, increasing substrate consumption by 19.3–21.4%. All vermicomposting treatments achieved maturity. VEB and VES treatments enhanced cellulase and β-glucosidase activities while reducing urease and nitrate reductase activities. Both VES and VEB increased the diversity of the intestinal microbiota in earthworm, with a notable enrichment of Bacteroidota and Proteobacteria. These treatments also promoted the enrichment of the nitrogen transforming genus as <i>Tyzzerella</i>, while suppressing methanotrophic, hydrocarbon degrading, and denitrifying functional taxa. Additionally, VES uniquely enriched the cellulose degrading genus <i>Dysgonomonas</i>. The variable communities in the earthworm gut under VES and VEB treatments were positively correlated with CEC/TOC and nitrate reductase activity. This study reveals that biochar and struvite may independently contributed to enhance carbon and nitrogen conversion efficiency and vermicompost maturity by modulating the variable microbial communities in the earthworm gut. These findings provide a theoretical basis and technical pathway for the coordinated regulation of carbon and nitrogen during the process of agricultural waste vermicomposting.</p> Graphical Abstract <p></p>