Abstract: Full-length cDNA of YB-1 gene was cloned from testicle in Small-tailed Han sheep by RT-PCR. pET32a expression system was used to express open reading frame (ORF) of YB-1 in E.coli with induction of IPTG at different concentrations. The low expression level of fusion protein revealed that IPTG concentration did not affect on its expression level. To improve the expression level of fusion protein, ampicillin was replaced by carbenicillin in cultural medium, which increased expression efficiency.