Histological methods were used to observe the sex differentiation of Pelteobagrus fulvidraco. It was shown that ovary differentiated before spermary under temperature of (20±1)℃. The anatomical indication of ovarian differentiation was the formation of ovarian cavity. Ovary began to form 13 days after hatching. The anatomical indication of spermary differentiation was the formation of spermaduct and seminiferous lobule, and spermary appeared 55 days after hatching. In the early period of development, germ cell division in the female was earlier than that in the male. The mitosis of oogonia appeared 25 days after hatching and the spermatogonia proliferated 55 days after hatching. Besides, the meiosis of oogonia appeared 34 days after hatching while the meiosis of spermatogonia began 64 days after hatching.