Abstract: With Sustained-release delivery systems of Chitin-Human Chorionic Gonadotropin (Chitin-HCG), at regular intervals after implantation of Chitin-HCG, we detected the gonadal developments, the levels of major sex hormones in serum and the relative expression levels of genes for reproduction endocrine function of female and male fish. The results showed that implanted the Chitin-HCG, the gonado-somatic index (GSI), levels of testosterone (T) and estradiol (E2) of female fish were more effective than the controlled group from the 6th day to the 30th day. The GSI of male fish was significantly higher than the controlled group only at the 6th day after implantation. The levels of testosterone (T) of male fish were significantly higher than the controlled group at the 2nd and the 14th day after implantation and the levels of estradiol (E2) of male fish showed no significant difference with the controlled group. With the RT-PCR, it showed that the content of the relative expression level of CYP19A mRNA was the most significant in gonad and the least significant in heart. The result of RT-PCR showed that the relative expression level of CYP19A mRNA in gonad of female fish was significantly higher than the controlled group at the 2nd and the 6th day after implantation, and that of the male fish was significantly higher than the controlled group at the 6th day after implantation. The relative expression level of ER mRNA in gonad of female fish was significantly higher than the controlled group from the 14th day to 30th day after implantation, and that of the male fish was significantly higher than the controlled group from the 6th day to the 21st day after implantation. In conclusion, after implantation of Chitin-HCG, the HCG can be released steadily and regularly in 21 days, promoting and regulating the reproduction endocrine function of fish.