Analysis on sex differentiation and gonadal development of Pristella maxillaris was conducted in the study by morphological, anatomical and histological methods. The results showed that different stages of oocytes could be observed at 6–month–old female fish, and a large number of sperm filled in seminiferous tubules of male testis. The sexual characteristics emerged with appearance of yellow granular structure in abdomen or the uplifted abdomen when fishes were over 4–month–old. Hook–shaped teeth were also observed in the anal fins of fishes over 100– day–old age, however, they could not be observed when fishes were in less two months. Based on the analysis from the gonads in 5 to 50 day–old fishes, it showed that there was no differentiated gonads in both sides of dorsal abdominal cavity at 10 days post–fertilization (dpf); later, there was germline cysts found in the abdominal cavity at 15 dpf, and the gonadal tissue was only spotted at one side of the abdominal cavity before 15 days. The ovary–like structure (‘juvenile ovary’) symmetrically appeared at 25 dpf and the baculiform testis appeared at 30 dpf. All these facts could provide a further study reference for sex differentiation, gonadal development and their regulative mechanism.