Biochar, a carbon-rich material derived from biomass pyrolysis, has high specific surface area, porous structure, and abundant functional groups, making it effective for adsorbing nitrogen and phosphorus in wastewater. This review summarizes the preparation, modification methods, and adsorption mechanisms of biochar for nitrogen and phosphorus removal, along with factors influencing its performance and future research directions. Biochar can be prepared through pyrolysis without chemical treatment or modified before or after pyrolysis using agents like FeCl₃, MgCl₂, or Ca(OH)₂. Chemical modification increases surface area, pore volume, and functional groups, enhancing adsorption capacity. Physical methods such as ball milling and steam activation also improve biochar's surface properties. Biological modification uses microorganisms to enhance functional groups on biochar surfaces. Nitrogen and phosphorus adsorption by biochar is influenced by raw materials, modification methods, pyrolysis conditions, pH, coexisting ions, temperature, and dosage. Biochar prepared from different biomass sources has varying adsorption capacities. Pyrolysis temperature affects surface area and pore volume, with optimal temperatures enhancing adsorption. pH significantly impacts adsorption, with biochar showing higher capacity at neutral to slightly alkaline conditions. Coexisting ions like CO₃²⁻, SO₄²⁻, and NO₃⁻ can either enhance or hinder adsorption through precipitation or competition for adsorption sites. Reaction temperature increases adsorption efficiency, especially for endothermic processes. Biochar dosage affects adsorption capacity, with optimal dosages maximizing removal efficiency. Biochar's adsorption capacity for nitrogen and phosphorus can be enhanced through modification, making it a promising material for wastewater treatment and environmental remediation. Future research should focus on optimizing biochar preparation and modification to improve adsorption efficiency and environmental sustainability.Biochar, a carbon-rich material derived from biomass pyrolysis, has high specific surface area, porous structure, and abundant functional groups, making it effective for adsorbing nitrogen and phosphorus in wastewater. This review summarizes the preparation, modification methods, and adsorption mechanisms of biochar for nitrogen and phosphorus removal, along with factors influencing its performance and future research directions. Biochar can be prepared through pyrolysis without chemical treatment or modified before or after pyrolysis using agents like FeCl₃, MgCl₂, or Ca(OH)₂. Chemical modification increases surface area, pore volume, and functional groups, enhancing adsorption capacity. Physical methods such as ball milling and steam activation also improve biochar's surface properties. Biological modification uses microorganisms to enhance functional groups on biochar surfaces. Nitrogen and phosphorus adsorption by biochar is influenced by raw materials, modification methods, pyrolysis conditions, pH, coexisting ions, temperature, and dosage. Biochar prepared from different biomass sources has varying adsorption capacities. Pyrolysis temperature affects surface area and pore volume, with optimal temperatures enhancing adsorption. pH significantly impacts adsorption, with biochar showing higher capacity at neutral to slightly alkaline conditions. Coexisting ions like CO₃²⁻, SO₄²⁻, and NO₃⁻ can either enhance or hinder adsorption through precipitation or competition for adsorption sites. Reaction temperature increases adsorption efficiency, especially for endothermic processes. Biochar dosage affects adsorption capacity, with optimal dosages maximizing removal efficiency. Biochar's adsorption capacity for nitrogen and phosphorus can be enhanced through modification, making it a promising material for wastewater treatment and environmental remediation. Future research should focus on optimizing biochar preparation and modification to improve adsorption efficiency and environmental sustainability.