Autophagy is a conserved intracellular degradation process that has been shown to have important biological implications in a variety of organisms. However, the study of autophagy in the plateau characteristic species of Bosgrunniens has hasn't been reported. Therefore, in order to explore the expression of autophagy-related genes in the reproductive process of yak under normal physiological conditions, the main reproductive organs (fallopian tubes, ovaries and uterus) of different breeding cycles (follicular phase, luteal phase and pregnancy) of yak were collected. Autophagy related 5 (Atg5) gene was cloned ，and analyzed by bioinformatics; qRT- PCR was used to detect the relative expression of Atg5 gene in tissues; Western blotting (West-blot, WB) was used to detect the expression of Atg5 and Atg5-Atg12 complex in different tissues; immunohistochemical method was used to analyze the distribution characteristics of Atg5 in various reproductive organs. We successfully cloned the yak Atg5 gene (GenBank: MK531791), which was highly conserved during the evolution process, and the encoded protein was a soluble non-transmembrane protein. The results of qRT-PCR and WB showed Atg5 and Atg5-Atg12 complex is expressed in the main reproductive organs of calves. The expression of Atg5-Atg12 in the ovarian follicles during follicular phase was significantly higher than that in the luteal phase and gestational phase, while the expression of Atg5 in the follicular phase was significantly lower than that in the luteal phase and gestational phase. The

expression of Atg5-Atg12 in the oviduct during luteal phase was significantly higher than that in the follicular phase and pregnancy. The expression of Atg5 in the fallopian tube during gestational phase was significantly higher than that in the follicular phase and the luteal phase. The expression of Atg5-Atg12 in the uterus during follicular phase and pregnancy was significantly higher than that in the luteal phase, while the expression of Atg5 in the uterus of the luteal phase is significantly higher than that during pregnancy and follicular phase. There was a negative correlation between the expression of Atg5 and Atg5-Atg12 at the protein level. Immunohistochemistry results showed that Atg5 was expressed in the oviductal mucosa epithelium, ovarian follicle membrane, granular layer, reproductive epithelium, luteal cells, endometrium and uterine gland. The results showed that autophagy was similar to other species in yak by detecting the expression of Atg 5 and Atg 12 in yak reproductive organs, and it was speculated that autophagy was involved in the regulation of yak reproductive physiology. The results of this study have implications for the study of autophagy in other large animals, specifically mammals in the alpine and hypoxic environment, and contribute to the study of autophagy involved in the reproductive physiology of other animals.