The objective of this study is to analyze the characteristics and differences of the testes morphology, vascular casts and arterial diameters in yak and cattle and to explore the physiological mechanism of plateau adaptability in yak testis. Twenty-eight testes from fourteen slaughtered adult yaks (Bos grunniens) and eighteen testes from nine slaughtered adult cattle (B. taurus) were collected in Xining, Qinghai Province, and their morphological parameters were examined, vascular casts were achieved by adopting the vessel perfusion technology, arterial diameters were measured, and all of data were analyzed using T-test. Results showed that there were differences in morphology (Table 1), arterial diameters of testis and epididymis between yak and cattle, and relative ratios of diameter of testicular artery or its branch to testis weight in yak was higher than that of cattle (P < 0.01) (Table 2). The general arterial architecture of yak testis was similar to that of the cattle. Additionally, there were fewer thick collecting veins and fine veins showed the compact woven bag-shaped arrangement on the surface of testis (Fig. 1). The study suggests that testicular vascular anatomical characteristics are the basis for supplying enough blood to yak testis, especially the compact woven bag-shaped veins arrangement is able to benefit for adjustment of temperature and sperm maturation, which might be one of the plateau adaptability characteristics of testis in yak.