Eutrophication caused by nitrogen, phosphorus and organic pollutants is a common problem which has attracted much attention in China. Ammonia nitrogen, as a main pollutant, should be removed efficiently to avoid the extension of eutrophication. In this research, Prussian Blue (PB), which can not only capture ammonia nitrogen by vacancy in crystal cell but also degrade organic pollutants by Fenton oxidation, was combined with modified biochar to increase efficiency of ammonia nitrogen removal. Several characterization methods were used to investigate the structure and morphologies of the biochar composite. Adsorption capacity of biochar composite material (BC700-PB) was tested by NH₄Cl solution. The results show that the maximum adsorption capacity to ammonia nitrogen is 24.4 mg/g and the removal efficiency is over 95% within 60 min under the condition of pH 8, which is 101.3% higher than that of the unmodified biochar. The adsorption mechanism of BC700-PB was investigated with Langmuir model and pseudo-second-order kinetic equation which reveal that the adsorption including physical adsorption by biochar and coordination adsorption by PB. Meanwhile, Fenton oxidation process is conducted by PB nanoparticles in the biochar composite material with existence of H₂O₂. The biochar composite material could catalyze H₂O₂ to generate ?OH, and achieve degradation of organic pollutants and adsorption of ammonia nitrogen. The PB/biochar composite material can be recycled easily by NaCl solution for several times. In conclusion, the PB/biochar composite is a promising material for eliminating multi-component eutrophication wastewater.