The early gonadal development and sexual differentiation of Rhynchocypris oxycephalus are described from the stage of hatching to 150 days after hatching. During this peroid, the average length of the body grew from 0.64 cm to 5.96 cm. the primordial germ cells (PGCs), which could be recognized at the time of hatching, began to protrude into peritoneal cavity at a standard total length of 1.91 cm. At a standard total length of 2.29cm, initial ovarian differentiation wasidentified by the transformation of PGCs to meiotic oocytes. Finally, at the standard total length of 5.96 cm, the female gonads gradually developed towards migratory nucleus oocytes, characterisiing the maturation. Oocytes proliferated rapidly after sex differentiation while the testis entered a period of quiescence, as they continued to multiply but did not undergo growth until the standard total length of 4.00 cm. At a standard total length of 4.00 cm, spermatocytes arrested in thephase of interkinesis, Sertoli-like cells and sperm duct formation, with signs of meiotic activity, were observed. Therefore it may be concluded that R. oxycephalus belongs to the differentiated type of gonochoristic teleosts.