Abstract: Agricultural nitrogen pollution has become a leading cause of non-point source pollution, resulting in widespread water quality deterioration including eutrophication, nitrate contamination of groundwater, and the formation of black and odorous water bodies. These adverse environmental impacts threaten aquatic ecosystems, public health, and hinder the advancement of rural ecological civilization. As agricultural production intensifies and expands, especially in rural areas lacking centralized treatment infrastructure, developing effective and sustainable nitrogen removal technologies is imperative for environmental protection. Constructed wetlands (CW) have been widely adopted as cost-effective, eco-friendly wastewater treatment systems that integrate physical, chemical, and biological processes for pollutant removal. Their low operational cost, landscape compatibility, and ability to support plant-microbe interactions make them particularly suitable for decentralized rural wastewater treatment. However, traditional CW often exhibit limited nitrogen removal efficiency and instability due to variable hydraulic loading, seasonal temperature fluctuations, and low carbon-to-nitrogen (C/N) ratios, which impede microbial nitrogen transformation processes. This review focuses on overcoming the challenges of nitrogen removal in CW by integrating functional substrates, including biochar, iron-based materials, and microbial fuel cells (MFC). These substrates enhance CW performance by improving substrate physicochemical properties, stimulating microbial communities, and facilitating nitrogen transformation under diverse environmental conditions. Biochar, produced by pyrolysis of biomass, is a porous carbonaceous material with high surface area and abundant functional groups, promoting pollutant adsorption and providing habitats for microorganisms. It improves redox potential and simultaneously supports aerobic nitrification and anaerobic denitrification. Iron-based materials, such as zero-valent iron and ferrous oxides, play crucial roles in redox reactions, facilitating denitrification and anaerobic ammonium oxidation (anammox). They also aid phosphorus adsorption and immobilize heavy metals, improving overall water quality. Combined application of biochar and iron synergistically enhances substrate stability and microbial diversity, promoting efficient nitrogen cycling and stronger plant-microbe interactions. MFC introduce bioelectrochemical functions by enabling extracellular electron transfer and electricity generation through microbial metabolism. They increase nitrogen removal efficiency, especially under low carbon availability, by stimulating microbial cooperation and redox activity. Though MFC effects on plant growth are limited, they provide added value by generating renewable energy to support system operation in off-grid rural settings. Furthermore, the use of these functional substrates helps to mitigate greenhouse gas emissions commonly associated with nitrogen cycling in wetlands, thereby contributing to climate change mitigation efforts. Their incorporation into CW design not only improves nitrogen removal but also enhances the overall ecological sustainability of treatment systems. Recent advances have demonstrated that combining these substrates with optimized operational parameters can significantly extend the lifespan and effectiveness of constructed wetlands, reduce maintenance costs and improve resilience to environmental fluctuations. his review synthesizes recent advances in the use of functional substrates for CW enhancement, elucidating their mechanisms, advantages under stress conditions, and practical implementation strategies. The integration of biochar, iron, and MFC offers a comprehensive and innovative approach to mitigate agricultural non-point source nitrogen pollution. Ultimately, this strategy improves nitrogen removal efficiency, system resilience, and sustainability, contributing significantly to water resource protection and rural ecological civilization development across diverse geographical regions worldwide with sustainable way.