[Objectives] This article aims to explore the adaptive mechanism of Tibetan Sheep Ovis arise epididymis in high-altitude environments. [Methods] The epididymal tissue and semen samples were collected from Tibetan Sheep in Haiyan County (at an altitude of approximately 3 500 m) and Xunhua County (at an altitude of approximately 2 300 m) in Qinghai Province. Sperm extraction, paraffin embedding and tissue sectioning, fluorescence quantitative PCR, Western blotting, and immunohistochemistry were employed to compare semen quality, epididymal histology, and expression and distribution of sperm maturation- associated genes PRDX2, STAR, and GALNTL5. The 2^﹣ΔΔCt method was adopted to calculate the relative mRNA level, and Western blot results were analyzed by Image J. The data were analyzed in SPSS 25.0. Independent sample t-test was performed to compare gene and protein expression levels between two altitudes, and one-way analysis of variance and multiple comparisons were performed among three different tissues. The results are expressed as mean ± SD. P < 0.05 indicates a significant difference. [Results] The semen quality of high-altitude Tibetan Sheep slightly decreased, while meeting the fertilization criteria (Table 3). High-altitude Tibetan Sheep had a smaller inner diameter of the lumen and thicker columnar epithelium at the tail of the epididymis (Table 4). PRDX2 was mainly expressed in epididymal epithelial cells, and its expression level was down-regulated in the epididymis of high-altitude Tibetan Sheep. STAR mainly existed in the principal cells of the epididymal epithelium, with up-regulated expression in the epididymis of high-altitude Tibetan Sheep. GALNTL5 was mainly located in the main and basal cells of the epididymis, and its expression level in the epididymis was up-regulated in high-altitude Tibetan Sheep (Figs. 2﹣4). [Conclusion] The differences in histology of epididymal tissue and semen quality between Tibetan Sheep at different altitudes are adaptive changes to high-altitude and low-oxygen environments. The down-regulated expression of PRDX2 as an antioxidant for sperm in the epididymis of high-altitude Tibetan Sheep is hypothesized to be due to the decrease in oxygen content in the epididymal environment under low-oxygen conditions. The upregulated expression of STAR in the epididymis of high-altitude Tibetan Sheep indicates that this protein promotes the synthesis of androgens to maintain the stability of the epididymal lumen environment under high-altitude and low-oxygen conditions. GALNTL5 as a starting enzyme for catalyzing the synthesis of glycoproteins is upregulated in the epididymis of high-altitude Tibetan Sheep, indicating that this protein promotes the synthesis of glycoproteins in the high-altitude and low-oxygen environment to maintain sperm maturation in the epididymis.