<p>Dissimilatory nitrate reduction to ammonium (DNRA) is an important pathway of nitrogen metabolism and is widely present in sewage, river sediments and soil. However, investigations into DNRA during composting processes remain sparse, particularly concerning the regulatory mechanisms involved. Therefore, this study aims to elucidate the influences of biotic and abiotic factors on DNRA within composting environments by employing metagenomic analyses to assess microbial community structures, functional gene distributions, and environmental parameters associated with fermentative DNRA (F-DNRA) and respiratory DNRA (R-DNRA). Results indicated that the microbial agents downregulated the relative abundance of F-DNRA functional genes (<i>nirBD</i>) while up-regulating R-DNRA functional genes (<i>nrfA</i>) by altering the physicochemical properties and microbial composition related to DNRA. Remarkably, the relative abundance of <i>nirBD</i> was observed to be 5.79 to 419.48 times greater than that of <i>nrfAH</i>, establishing F-DNRA as the predominant pathway for DNRA during composting. Furthermore, <i>Streptomyces</i> was the dominant genus associated with F-DNRA. Correlation analyses identified dissolved organic carbon as a principal factor influencing both <i>nirBD</i> and <i>nrfAH</i>. Network analyses highlighted a mutualistic relationship between DNRA microorganisms. These insights provide a foundational understanding for the regulation of DNRA processes, enhancing our comprehension of nitrogen metabolism dynamics within composting systems.</p>