This study investigates the effect of MnO₂-biochar composites (MBC) on promoting humification during chicken manure composting. The addition of MBC significantly increased both humus and humic acid (HA) concentrations by 29.1% and 37.2%, respectively, compared to the control group (CK). MBC also improved the stability of compost products. Hetero two-dimensional correlation spectra revealed that MBC altered the formation mechanism of humus fractions during composting. Random forest analysis identified *Microbacterium*, *Bacteroides*, *Kroppenstedtia*, *Gracilibacillus*, and *Lentibacillus* as key genera significantly related to humus formation. These genera were enhanced in abundance during composting, contributing to the direct transformation of organic components into macromolecular humus structures. The structural equation model confirmed that these genera indirectly influenced humus formation through the production of aromatic compounds via secondary metabolism. The findings highlight the potential of MBC in effectively promoting humification and harmless disposal of hazardous biowastes through composting.This study investigates the effect of MnO₂-biochar composites (MBC) on promoting humification during chicken manure composting. The addition of MBC significantly increased both humus and humic acid (HA) concentrations by 29.1% and 37.2%, respectively, compared to the control group (CK). MBC also improved the stability of compost products. Hetero two-dimensional correlation spectra revealed that MBC altered the formation mechanism of humus fractions during composting. Random forest analysis identified *Microbacterium*, *Bacteroides*, *Kroppenstedtia*, *Gracilibacillus*, and *Lentibacillus* as key genera significantly related to humus formation. These genera were enhanced in abundance during composting, contributing to the direct transformation of organic components into macromolecular humus structures. The structural equation model confirmed that these genera indirectly influenced humus formation through the production of aromatic compounds via secondary metabolism. The findings highlight the potential of MBC in effectively promoting humification and harmless disposal of hazardous biowastes through composting.