The reproductive toxicity of Aroclor 1254 on the oogenesis, the fertilization and preimplantion embryonic in vivo in female mice, the spermatogenesis toxicity, the sperma fertilizing ability and the zygote developmental toxicity in vivo in male mice were studied, and the toxicity mechanism were discussed by histopathological examination of the ovary, the uterus, the testis and epididymides. Aroclor 1254 was diluted by sterilized peanut oil, then injected into mouse abdominal cavity, with dosages of 1/10,1/50,l/250,and 1/1250 LD50 .Mice injected the peanut oil only were used as control. The females and males in puberty and weaning period were exposure directly to Aroclor 1254; The females in lactation and pregnancy period were exposure directly to Aroclor 1254 so that the infants and the fetus were exposure indirectly to Aroclor 1254.With the increasingly of the dosages, the ovulations of the females exposure to Aroclor 1254 in every period showed a decreasing trend, the ovulation number of the females exposure to Aroclor 1254 were decreased significantly in puberty and the fetal period, between other groups and control group was no statistics difference. Histopathology observation of ovaries revealed that the ovulations decreased in females may be due to the follicular tresia. If the fertilization could be finished, a majority of the zygote can finish the first cleavage and develop into 2-cell embryo. But the fertility rate of the females exposure to Aroclor 1254 shown a marked decreased in puberty and the fetal period, between other groups and control group was no statistics difference. The toxicity effect of Aroclor 1254 behaved principally in farther development process of 2-cell embryo, the ratio of embryo development into morale and blastocysts was significantly decreased with the increasing of the dosages, but the ratio ofdevelopment relayed and degeneration embryo was significantly increased. The main reason was that the toxicity effect of Aroclor 1254 directly, and resulted in the structure anomaly,inflammation reaction and pathology transformation of the reproductive organ, so that did not enable to normal development embryo, and made development stopping or degeneration. In addition, an appearance of follicular development in ovarian and corpus luteum development relayed in influenced females, this also might made embryo development relayed and degeneration.The males in puberty were exposure to Aroclor 1254, the toxicity effect of Aroclor 1254 resulted in the structure damage and cell pathological changes of the test's, and the toxicity effect of Aroclor 1254 on spermatogenesis focused mainly on the sphere sperm cell development and sperm maturity. With the increasing of the dosages, the sperm motility was decreased significantly. The ratio of abnormity sperm and abnormal acrosome sperm were increased significantly, and the effect on the sperm density was lower. In the mice that in the suckling period were exposure to Aroclor 1254,. the toxicity effect of Aroclor 1254 directly and resulted in the pathological changes of the sexual gland, influenced the nutrient accumulation and maturity division of the spermatocyte , the sphere sperm cell development and sperm maturity. The sperm density of the males in 1/10 LDso dosages group was decreased significantly, and with the increasing of the dosages, the sperm motility was decreased significantly, the ratio of the deformation sperm and the acrosome abnormal sperm was increased significantly. The males in the suckling and fetal period were exposure to Aroclor 1254, Aroclor 1254 disturbed the division proliferation of reproductive cell and the nutrient accumulation of the spermatocyte, so that the number of the reproductive cell in the maturation period was decreased. The sperm density was decreased significantly with the increasingly of the dosages. Owing to placenta and milk transshipping effect, the content of Aroclor 1254 in fetal and infant vivo was very low, so there were not significantly pathological changes in sexual gland, the effect of Aroclor