Aiming to explore the feasibility of using cotton stalk biochar for purifying kitchen waste biogas slurry and recovering nitrogen and phosphorus nutrients, and clarify the regulatory role of pyrolysis temperature on the adsorption performance of biochar, it prepared cotton stalk biochar at different pyrolysis temperatures (300℃, 400℃, 500℃, 600℃, and 700℃). The physicochemical structures of the biochar were systematically characterized, and its adsorption performance for ammonia nitrogen, nitrate nitrogen, total nitrogen, total phosphorus, and chemical oxygen demand ( COD specifically referred to the amount of reducing substances determined by chemical oxidation) in simulated biogas slurry was investigated. The biochar with optimal comprehensive performance was selected for dosage gradient experiments to explore its removal efficiency of pollutants from actual biogas slurry and determine the optimal dosage threshold. The results indicated that pyrolysis temperature significantly regulated the physicochemical properties and adsorption behavior of the biochar. Biochar prepared at 600℃exhibited the highest adsorption capacity for ammonia nitrogen and COD, with values of 8.65mg/g and 181.02mg/g, respectively. Biochar prepared at 500℃ demonstrated the best removal performance for nitrate nitrogen and total nitrogen, with adsorption capacities of 27.0mg/g and 68.66mg/g, respectively. Biochar prepared at 700℃ showed the highest adsorption capacity for total phosphorus, reaching 3.36mg/g. Although biochar prepared at 500℃ was not the optimal adsorbent for any single pollutant, it possessed the most balanced comprehensive adsorption performance, characterized by welldeveloped pore structure and suitable oxygen-containing functional groups, making it a promising candidate for the treatment of actual biogas slurry. Kinetic analysis revealed that the removal of ammonia nitrogen, nitrate nitrogen, total nitrogen, and COD was dominated by physical adsorption, consistent with the pseudo-first-order kinetic model, whereas the removal of total phosphorus was primarily governed by chemical precipitation and complexation, fitting better with the pseudo-second-order kinetic model. In the application to actual biogas slurry, as the dosage of the optimal biochar increased from 1g to 2g, the removal rates of all pollutants continued to increase, while the adsorption capacity per unit mass decreased. When the dosage reached 1.5g, the increase in removal rates slowed significantly, indicating that the optimal dosage threshold for this system was 1.5g. Considering both adsorption performance and material economy, the biochar prepared at 500℃ demonstrated good engineering application potential for the adsorptive treatment of biogas slurry at a dosage of 1.5g.