NOVELTY - Production of biogas and recovery of phosphorus involves feeding chicken manure into fermentation tank (t1), carrying out anaerobic fermentation, separating, generating biogas (b1) and feed solution (s1), carrying out anaerobic fermentation process, adding obtained biogas (b3) to high-temperature digester, adding the obtained feed solutions to reactor, adding magnesium source, aerating, adding resultant product to mixer, adding product of high-temperature digester, parasite egg and pathogenic microorganisms, mixing, and obtaining slow-release magnesium ammonium phosphate fertilizer.    USE - Production of biogas and recovery of phosphorus (claimed).    ADVANTAGE - The method enables efficient production of biogas and recovery of phosphorus with high yield by reducing suppression effect of high-concentration ammonia nitrogen generated in the chicken manure fermentation process on anaerobic microorganism, and improving nitrogen and phosphorus concentration in the anaerobic fermentation material liquid.    DETAILED DESCRIPTION - Production of biogas and recovery of phosphorus involves feeding chicken manure into fermentation tank (t1), carrying out anaerobic fermentation process, providing resultant product into solid-liquid separating machine (m1), separating, generating biogas (b1) and feed solution (s1), adding biogas (b1) to fermentation tank (t2), carrying out anaerobic methane fermentation process, providing resultant product into solid-liquid separating machine (m2), generating biogas (b2) and feed solution (s2), adding biogas (b2) to fermentation tank (t3), adding nutrient solution, mixing, carrying out anaerobic methane fermentation process, providing resultant product into solid-liquid separating machine (m3), generating biogas (b3) and feed solution (s3), adding biogas (b3) to high-temperature digester, carrying out high-temperature digestion, adding the obtained feed solutions to reactor, adding magnesium source as precipitating agent, aerating, stripping carbon dioxide, producing magnesium ammonium phosphate as crystalline product main component, adding resultant product to mixer, adding product of high-temperature digester, parasite egg and pathogenic microorganisms, mixing, adding resultant mixture to fertilizer granulating machine, adding the formed granular fertilizer to drying machine, and obtaining slow-release magnesium ammonium phosphate fertilizer.