Abstract: The expression level of SYCP3 in yak and cattle-yak was studied by RT-PCR and real-time quantitative PCR in this paper. The results showed that SYCP3 was specifc expressed in yak testis, and the difference of expression level between yak and cattle-yak was extremely remarkable (P<0.01).The tissue sections of testis and epididymis showed that there wasn’t secondary spermatocytes or spermatids in cattleyak testis, and sperm could’t be observed in the epididymis. However, there were all levels of spermatogenic cells in yak testis, and sperms grew well in epididymis which was the same represent as man and mice lack or low express with SYCP3. SYCP3 gene was likely to have a relationship with male infertility of cattle-yak.