Abstract: In order to optimize the biological nitrogen removal process of ABS resin wastewater, the denitrification potentials of the wastewater were measured, and the degradation characteristics of organics in the wastewater during the denitrification process were investigated. The results indicated that ABS resin wastewater contained sufficient carbon source for its denitrification including both readily biodegradable and slowly biodegradable organics with different denitrification rates. For ABS resin wastewater with soluble chemical oxygen demand (SCOD) of 755.4-1043.3 mg/L and total nitrogen (TN) of86.1-111.1 mg/L, the total denitrification potentials were from 95.4-144.6 mg/L (NO₃^--N). The denitrification potentials of the readily biodegradable organics in the wastewater were from 33.2-49.7 mg/L with denitrification rates of 3.4-4.6 mg/(g·h) (NO₃^--N). The total denitrification potentials of the two categories of slowly biodegradable organics ranged from 62.2-94.9 mg/L with denitrification rates of 2.2-3.2 and 0.4-0.9 mg/(g·h), respectively. During the denitrification process, the removal efficiencies of SCOD and organic nitrogen (ON) were from 48.9%-62.8% and 81.5%-95.7%, respectively. Organics containing nitrogen including organic nitriles, were the important carbon sources for denitrification and were degraded significantly with production of ammonia nitrogen. According to three-dimensional excitation and emission matrix fluorescence spectra,the aromatic cycles were not destroyed significantly under denitrificantion conditions, while they were destroyed quickly under aerobic conditions.