To explore the influence of different extractant (1 mol/L KCl, 2 mol/L KCl, 4 mol/L KCl and 0.01 mol/L CaCl₂) and ratio of water to sediment (5:1, 10:1, 50:1 and 100:1) on the determination of extractable nitrogen in sediments from an urban polluted river, surface sediments of Jiuxiang River in Xianlin university town of Nanjing was used in the experiment. Result showed that KCl extract nitrogen more effectively than CaCl₂. The amount of NH₄⁺-N extracted by KCl and CaCl₂ ranged from 312.17 mg/kg to 479.23 mg/kg and 177.52 mg/kg to 339.31 mg/kg, respectively, while NO₃^--N extracted by them ranged from 4.49 mg/kg to 21.56 mg/kg and 4.25 mg/kg to 8.53 mg/kg, respectively. The amount of extractable nitrogen increased with water-sediment ratios. In the experiment group of 1 mol/L KCl, the extract amount of NH₄⁺-N and NO₃^--N increased by 41.97% and 187.08%when the ratio of water to sediment ranged from 5:1 to 100:1, respectively. The amount of NH₄⁺-N extracted increased with higher extractant concentrations, while NO₃^--N decreased with lower ones. The experiment suggested that 1 mol/L KCl as extractant and the water-sediment ratio of 100:1 make a better combination when using for extracting NH₄⁺-N and NO₃^--N from the urban river sediment.