[Objective] The ovary microstructure and the changes of the follicle during the development period of blue fox during the estrous period were studied.[Method] Ten left ovaries were collected from 10 female blue foxes during the estrous period. The histological structure of the ovary and follicular development process were observed by using optical microscope. And 30 primordial follicles, 30 primary follicles, 15 growing follicles, 15 vesicular follicle, 15 mature follicles and the oocytes in the follicles of different developing stages were measured and photographed by eyepiece micrometer and photomicrographic technique respectively. [Result] The ovary of blue fox consisted of germinal epithelium, tunica albuginea, cortex and medulla. The cor- tex, which was located at the periphery of the ovary, contained many interstitial cells and follicles at different developing stages. Medulla was located below the cortex, with a lot of blood vessels. The diameters of follicles at different developmental stages and oocytes had greater differences during the developmental period of follicle. The diameter of follicles was 45.45-974.55 μm and the diameter of oocytes was 30.23-147.27 μm. The zona pellucida appeared at the primary follicle stage. The atresia of follicles occurred at all the developmental stages of follicle and the main manifestations were the shrunk oocyte and karyon, and loose and degraded granular cells. [Conclusion] The research provided histological basis for revealing the reproductive mechanism of female blue fox.
