The histology of the gonadal development of Gymnocypris selincuoensis , an endemic fish in Selincuo Lake, Northern Tibet , was studied. The development of ovary and testis was composed of Ⅵstages . The oogenesis was composed of 5 phases : 1. oogonia; 2. oocyte with follicular epithelium consisting of single layer of follicle cells; 3. oocyte with vesicles; 4. oocyte filled with yolk; 5. mature oocyte. In the later phase 2 of development of oocytes , the yolk nucleus , which was probably related to the formation of yolk , broke up and formed a ring in the outer cortex. From the later phase 2 to the middle phase 3 of development of oocytes , the nucleolar bodies extruded into cytoplasm nucleolar bodies with cytoplasm would helpful to the process of yolk formation. From the phase 2 to the early phase 4 of oocytes , there was a transparent layer in the outboard of nuclear membrane. From the early phase 3 of oocyte , between oocyte membrane and follicular layer presented zona radiata which is mostly formed by oocyte. After spawning , a few mature oocytes became astrophied and were re2absorbed subsequently in ovary. The spawning season which was evidenced by histology of oocytes and investigation of field work, extends from early April to early August. In a reproductive season, the ovary of selincuo naked carp matured only once in a year.