Abstract: Acute toxicity tests of four new pesticides were conducted in the lab with Scenedesmus obliquus,Daphnia magna and Brachydanio rerio as subject to evaluate the safety of pesticides in the aquatic ecosystem.Results showed that acetamiprid as pesticide was extremely toxic to Daphnia magna,highly toxic to Brachydanio rerio and low toxic to Scenedesmus obliquus;pymetrozine as pesticide was low toxic to Daphnia magna and Brachydanio rerio,but moderately toxic to Scenedesmus obliquus;oxadiazon as herbicide is highly toxic to Scenedesmus obliquus,but moderately toxic to Daphnia magna and Brachydanio rerio;quizalofop-p-ethyl as herbicide was highly toxic to Scenedesmus obliquus and Brachydanio rerio,but moderately toxic to Daphnia magna.

Key words: acetamiprid, pymetrozine, oxadiazon, quizalofop-p-ethyl, Scenedesmus obliquus, Daphnia magna, Brachydanio rerio, safety evaluation