Di(2-ethylhexyl) phthalate (DEHP) is one of the phthalate esters which is widely used as a plasticizer in industrial products, personal care products and pharmaceutical products. Due to its tendency to enter the environment during the process of use and cause endocrine disrupting effects, the use of DEHP has been widely limited. DnOP and DIOP are two isomers of DEHP, which the use of both is not strictly restricted. The global outbreak of COVID-19 has led to a surge in the use of plastic protective products such as masks, which may lead to increased concentrations of PAEs in the environment. The lack of information of DnOP and DIOP may lead to potential risks. A multigenerational experiment was designed by us to verify the differences in the toxicity of DEHP, DnOP, and DIOP to Daphnia magna. The results showed that the mortality rate of Daphnia magna exposed to both isomers was significantly higher than that of DEHP with the increase of exposure concentration and time, showing a strong lethal effect. Decreased body length, delayed time to first brood, reduced offspring and reproduction of Daphnia magna were observed after treatment with three PAEs, while no obvious effects on the body length of brood were observed. After two generations of exposure, Daphnia Magna could not recover significantly within 21 days. We used intrinsic growth rate and Leslie matrix to evaluate the effect of PAEs on the Daphnia magna population, and the PNEC values of DEHP, DnOP and DIOP based on population were 2.80, 0.36 and 0.55 μg·L-1, respectively. Our research indicated that unconcerned isomers are potentially more toxic to the Daphnia magna population than DEHP at environmentally relevant concentrations.