Abstract: Pesticides have been paid attention during recent years because of their ubiquity and persistence in the environment and their important biological effects. In this study, the species sensitivity distribution model for atrazine, one widely used herbicide, was developed using a log-logistic distribution based on the acute and chronic toxicity data across various trophic levels. Furthermore, aquatic species sensitivities to atrazine were compared between different taxa and regions, and 5% hazardous concentration of the species (HC₅) of different taxa and regions were derived based on the species sensitivity distribution models. The results showed that there were significant differences between aquatic animals and aquatic plants, vertebrates (including fish and amphibians) and invertebrates (including crustaceans, insects, mollusks and worms). HC_5values for acute toxicity to aquatic animals and aquatic plants were 4257.94and 12.55μg/L; to vertebrates, invertebrates, fishes, crustaceans were 7490.31,1.76,9.90and 1201.16μg/L, respectively. HC_5for chronic toxicity to aquatic animals and aquatic plants were 2.47and 1.95μg/L, respectively. The sensitivity of different taxa to atrazine followed the order of aquatic plants > aquatic animals, invertebrates > vertebrates, crustaceans > fishes. Statistically, there was slightly difference between sensitivity distribution of the Chinese and American aquatic animals to atrazine. However, the species sensitivities to atrazine are different between China and America since these two countries have different representative species.