The objective of this study was to determine and assess niclosamide residue levels in the Nan Ji Shan island within Poyang Lake Region, from March to June, September, October and December of 2012. Water and sediment samples from the Nan Ji Shan island were extracted with alkaline ethylacetate,and were detected by high performance liquid chromatography (HPLC). Niclosamide residues were detected in all water and sediment samples in varying concentrations during the two periods using molluscicide, niclosamide residues concentration water samples ranged from 0.01 to 0.038 mg/L, and from 0.1 to 0.473 mg/kg in sediments. According to the guidelines for potential risk assessment drawn up by the US Environmental Protection Agency, the risk of niclosamide residue was assessed. The results indicated that it would cause greater effect on fish, invertebrates and aquatic plants, but the influence on human and avian was relatively smaller.