The 21d chronic toxic effects of Zn and Cd in sediments on benthic organisms were investigated by using Misgurnus anguillicaudatus, Bellamya aeruginosa and Corbicula fluminea as the testing organisms, using mortality rate, bleeding rate, average body weight change, sluggishness rate and burrowing rate as the testing indexes, and verified by the sediment reference values of Zn and Cd in Lake Poyang. The results showed that the toxicity of Cd to benthic organisms in sediments was stronger than that of Zn, and the LC₅₀(50% lethal concentration) of Zn and Cd to Misgurnus anguillicaudatus, Bellamya aeruginosa and Corbicula fluminea were 644 and 61 mg/kg, 751 and 54 mg/kg, 652 and 81 mg/kg, and the EC₅₀(50% effective concentration) values were 526 and 49 mg/kg, 589 and 35 mg/kg, 474 and 45 mg/kg, respectively. It has been verified that the TEL (threshold effect level) and PEL (probable effect level) values of the sediments Zn and Cd are reasonable and have certain applicability. When the additive concentration of Zn and Cd is lower than the TEL value, Q_TEL<1 is not toxic. When the additive concentration was higher than PEL value, Q_PEL>1 showed obvious toxicity.