Ammonia nitrogen is one of the primary pollutants responsible for aquatic eutrophication. Low temperatures significantly inhibit the biological nitrogen removal performance in wastewater treatment plants, leading to elevated effluent ammonia concentrations and posing risks to the ecological security of receiving water bodies. This paper provides a comprehensive review of the major challenges confronting biological nitrogen removal under low-temperature conditions and the corresponding enhancement technologies, while also delving into the cold-response characteristics and potential cold-adaptation mechanisms of functional denitrifying microorganisms. Key findings indicate that low temperatures (<15 ℃) induce reduced cell membrane fluidity, decreased enzyme activity, and microbial community structure imbalance, thereby severely compromising nitrogen removal efficiency. Strategies such as process parameter optimization (e.g., extending hydraulic retention time, regulating dissolved oxygen and carbon dosage), development of functional carriers, quorum sensing-based microbial community regulation, and inoculation of cold-adapted microbial agents can effectively mitigate low-temperature inhibition. Cold-adapted microorganisms employ strategies including modulating membrane composition, synthesizing cold-adapted enzymes and cold-shock proteins, and secreting extracellular polymeric substances (EPS) to withstand cold stress. Notably, ammonia-oxidizing archaea, complete ammonia oxidizers (Comammox), and heterotrophic nitrification-aerobic denitrification bacteria exhibit significant competitive advantages over conventional ammonia-oxidizing bacteria at low temperatures. Future research should prioritize the development of cost-effective immobilization and retention techniques for microbial agents, design of novel functional carriers based on nanomaterials or bionic structures, in-depth elucidation of the cold-adaptation mechanisms and interspecies synergistic metabolic pathways of Comammox, and systematic dissection of cold-regulatory networks using multi-omics approaches (metagenomics, transcriptomics, etc.). Furthermore, exploring integrated processes such as bioaugmentation coupled with electrochemistry is essential to achieve long-term, efficient, and economically stable operation of nitrogen removal systems in cold regions, providing robust theoretical support and technical guidance for wastewater treatment in low-temperature environments.