The aim of this study was to investigate the median lethal concentration (LC50)of six chemicals on swamp eel (Anguilla marmorata) elver under two controlled temperatures, 20 ℃ and 30 ℃. Commonly used concentrations of agents were also examined for swamp eel. Under 20 ℃, the 96 hour LC50 values of copper sulfate, potassium permanganate, formalin, Masoten, iodine preparation and Benzalkonium chloride (BKC) were 3.90, 1.75, 146.44, 5.46, 0.80, and 7.02 ppm, respectively. When temperature was 30oC, their LC50 values were 3.06, 1.65, 131.46, 1.41, 0.69, and 6.91 ppm, respectively. These indicated that the agents were more toxic to the fish at 30 ℃ than at 20 ℃. The relative toxicity of iodine preparation was stronger than the other agents. The relative toxicity of agents was in the following order: potassium permanganate, Masoten, copper sulfate, BKC, and formalin at 20 ℃ and Masoten, potassium permanganate, copper sulfate, BKC, and formalin at 30 ℃. The results also showed that the commonly used concentration of 50-200 ppm iodine preparation for 10-15 min and 3-5 ppm potassium permanganate for long-term exposure were not suitable to swamp eel. Moreover, the exposure duration of 8, 100 and 500 ppm copper sulfate for 30, 20 and 1 min, 100 ppm Masoten for 60 min, 20 ppm potassium permanganate for 20 min, 200, 250 and 400 ppm formalin for 60, 30, and 15 min, respectively were suitable.