Abstract: The endocrine disruption effect of four permethrin isomers to the chorion carcinoma JEG-3 cells was investigated. JEG-3 cell lines was employed as the in vitro model and the potential risks of these compounds to maternal-fetal health were also evaluated. Four permethrin isomers were separated by HPLC. The results of real-time reverse transcription polymerase chain reaction (RT-PCR) revealed that those four isomers, in RNA levels, exhibited selective influence on the relative expression amounts of the genes correspounding to gonadotropin-releasing hormone (GnRH) and its receptor, the enzymes of the steroidogenesis pathway and human leucocyte antigen G (HLA-G). The endocrine disruption effects induced by 1R-cis-PM and 1S-trans-PM were more significant than that induced by 1S-cis-PM and 1R-trans-PM.