Abstract: The acute and chronic reproductive toxicity of four kinds of alkyl phenolic compounds to Daphnia magna were determined.The 24 h biologic acute and 21 d reproductive experiments were taken to discuss the relationship between quantitative structure and effect of the compounds.The result showed that all the measured compounds have effect on the reproduction of the daphnia.Two kinds of compounds,4-octylphenol and 4-nonylphenol,not only decrease the number of the organism reproduction,but also affect the parthenogenetic phenomena of the daphnia.The regressive relationship between the molecular connectivity and the bio-toxicity is established availably,and nucleophilic reaction may be the main mechanism of the compounds.