Abstract: Environmental hormones and endocrine-disrupting chemicals, are outside factors, which can interfere in the normal function of natural hormone, suc h as production, release, transport, metabolism, link, effect or exclusion. These polluters disordering estrogen and reproduction could link with estrogen receptor and even produce estrogen effects. As a typical kind of environmental hormones, polychlorinated biphenyls(PCBs) are a class of chlorinated hydrocarbon compounds with high chemical stabilities and toxicity, and often extant in environment and bio-accumulated in food chains, leading to a ubiquitous contamination in nature and man. In laboratory studies, technical PCB mixtures have been shown to cause reproductive disorders in fish. But the interferential mechanism of PCB was not found, the aim of the present study was to provide the research of the mechanism with the effects of PCB₁₂₅₄ on testosterone and estradiol of serum and culture ovary in allogynogenetic silver crucian carp. The effects of PCB₁₂₅₄ on sex steroids in allogynogenetic silver crucian carp were investigated by using in vitro injection of PCB₁₂₅₄ 0.5, 5, 50 μg·kg^-1body weight. In injection groups, the levels of testosterone in the serum decreased with time and concentration of PCB₁₂₅₄. Meanwhile, the levels of estradiol in the serum changed in the opposite trend. In the groups of incubated ovarian fragments in vitro with PCB₁₂₅₄, the levels of estradiol secretion from ovary increased with time and concentration of PCB₁₂₅₄ treatments.