Abstract: To investigate the fermentation characteristics and bacterial community dynamics during co-composting of Perilla leaf herbal residue and Pleurotus eryngii mushroom residue, this study established composting piles with a mass ratio of 10:1 (herbal residue:mushroom residue), adjusted the C/N ratio to 25:1 by adding cattle manure, and conducted an 80-day natural fermentation experiment. Dynamic changes in temperature, moisture, pH, electrical conductivity (EC), physical properties (bulk density, total porosity, aeration porosity, water-holding porosity), nutrient content (organic matter, alkali-hydrolyzable nitrogen, available phosphorus, available potassium, humus), and seed germination index (GI) were monitored. Bacterial community succession was analyzed via 16S rRNA gene sequencing. The results showed: 1) The composting process included four phases: heating-up period (1–4 d), high-temperature period (5–41 d), cooling-down period (42–60 d), and maturation period (61–80 d). During the maturation period, temperature stabilized at ambient levels, pH increased to 8.1–8.3, EC fluctuated between 4.8 and 5.3 mS/cm, and GI recovered to 93.5% (initial: 62.3%; high-temperature phase: 52.1%). Bulk density increased from 0.26 to 0.34 g/cm³, water-holding porosity rose from 40.1% to 46.2%, while total porosity and aeration porosity decreased from 71.3% and 31.2% to 66.2% and 20.5%, respectively. Alkali-hydrolyzable nitrogen, available phosphorus, available potassium, and humus content significantly increased (P<0.05) from initial 2.23, 0.29, 0.72, and 302.5 g/kg to 2.75, 0.34, 0.85, and 344.6 g/kg at the maturation period (increases of 25.1%, 18.1%, 17.2%, and 13.9%, respectively), whereas organic matter content decreased by 8.7%. 2) Bacterial diversity indices (Chao1 and Shannon) significantly increased (P<0.05), accompanied by phased succession of community structure: Firmicutes dominated the heating-up phase (>65% relative abundance), Proteobacteria became predominant during the high-temperature phase, Firmicutes and Thermotogae prevailed in the cooling-down phase, and Actinobacteria, Firmicutes, and Bacteroidetes emerged as dominant phyla in the maturation phase. 3) Spearman correlation analysis revealed that Firmicutes was negatively correlated with moisture content, Actinobacteria positively correlated with EC, Proteobacteria negatively correlated with EC, and Bacteroidetes positively correlated with pH. These findings demonstrate stage-specific physicochemical parameter dynamics, enhanced bacterial diversity and uniformity, and tight interactions between dominant microbial taxa and composting environments. Optimizing environmental conditions to favor functional bacterial communities at different stages could improve compost quality, providing theoretical guidance for agricultural waste recycling.