NOVELTY - Removal of nitrogen-sulfur compound from biogas fermentation wastewater involves acidifying biogas fermentation wastewater, adjusting pH to 7-8, adding oxidizing agent, stirring, adding mixture of octadecylamine and absolute ethanol, adding resultant product to high-pressure reactor, stirring, adding organic solvent, sealing, stirring, adding benzyl methane, replacing air in the reactor with inert gas, reacting, washing resultant product with anhydrous ethanol, adding extracting agent to resultant pretreated wastewater, extracting, aerating, stirring for 15 minutes, and filtering.    USE - Removal of nitrogen-sulfur compound from biogas fermentation wastewater (claimed).    ADVANTAGE - The method enables simple, quick, environmentally-friendly, stable, efficient and economical removal of nitrogen-sulfur compound from biogas fermentation wastewater at high recycling rate, with reduced energy consumption.    DETAILED DESCRIPTION - Removal of nitrogen-sulfur compound from biogas fermentation wastewater involves acidifying biogas fermentation wastewater at 28-32 degrees C, adjusting pH to 7-8, adding 0.4-0.6% oxidizing agent, stirring, adding mixture of octadecylamine and absolute ethanol in a weight ratio of 1:3-5, adding resultant product to high-pressure reactor, stirring, adding organic solvent in an amount of 4 times the volume of absolute ethanol, sealing, replacing air in the reactor with inert gas at 6-7 MPa 3-5 times, stirring for 55-65 minutes, maintaining at 80-85 degrees C for 3-4 hours, distilling off absolute ethanol under reduced pressure, adding benzyl methane, replacing air in the reactor with inert gas 3-5 times, reacting at 80-85 degrees C for 6-8 hours, washing resultant product with anhydrous ethanol, distilling off absolute ethanol under reduced pressure, adding extracting agent to resultant pretreated wastewater in a weight ratio of 1:600-700, extracting, aerating, stirring for 15 minutes, and filtering by adsorption filtration apparatus at adsorption flow of 4-5 L/minute.