<p>This study presents a novel strategy for the efficient remediation of hexavalent chromium (Cr(VI)) in water and soil by immobilizing a fusion strain F14 on a novel montmorillonite-Fe magnetic biochar (FeMB). The primary novelty of this work lies in the preparation of FeMB by incorporating clay mineral montmorillonite and an iron source with corn straw, which significantly enhances the biochar carrier’s stability and its adsorption capacity for heavy metals, while simultaneously imparting magnetic properties for easy recovery. Characterization indicates that FeMB effectively loads iron oxide particles, which are pivotal for the adsorption and reduction of Cr(VI) to the less toxic Cr(III) form. The immobilized pellets (F14-FeMB-SA) surpassed free bacteria and other immobilized forms, achieving an impressive 88.37% Cr(VI) removal rate in soil. Additionally, the study demonstrates that the immobilized pellets markedly elevate soil enzyme activities, implying enhanced microbial activity and improved soil health. The remediation mechanism initiates with the adsorption of Cr(VI) onto FeMB, followed by its reduction to Cr(III) and subsequent microbial adsorption within the pellets. This research provides a new material design concept and a solid theoretical foundation for the application of immobilized microbial technology in the remediation of heavy metal-contaminated soils.</p>