Abstract: Protein phosphatase 2 A（PP2 A） has the function of reversing protein kinase, and plays a certain role in regulating the phosphorylation signal pathway. Because cyclin-dependent protein kinases（CDKs） play an important role in the process of spermatogenesis, PP2 A is capable of influencing the activity of CDK through dephosphorylation, namely, PP2 A may have an effect on the process of spermatogenesis, and thus PP2 A is speculated to be related to male infertile of cattleyak. In order to verify whether PP2 A is involved in the development of spermatogenesis and has an impact on it, the CDs region sequence of PP2 A was cloned from the testes of cattle-yak in this study, and bioinformatics analysis was carried out on it. Meanwhile, Q-PCR was used to detect the expression of PP2 A gene in the testes and epididymis of yak and cattle-yak. The results showed that the CDs region of cattle-yak PP2 A gene had an encoding length of 930 bp, and the 309 amino acid sequences encoded were conservative, with negative acid hydrophilic stable protein. The homology with artiodactyla was higher and the distance was closer in phylogenetic tree. It was not a secretory protein but a binding transporter and had no transmembrane domain. The expression of PP2 A in yak was significantly higher in both testis and epididymis than in cattle-yak（P＜0.01）, and the expression of PP2 A in the testis and epididymis of cattle-yak was down-regulated, suggesting that the significant down-regulation of PP2 A gene in cattleyak may have certain influences on some important signaling pathways and further contribute to the spermatogenesis of cattle-yak and PP2 A is related to male infertile of cattle-yak.