Abstract: In this research, four Chinese Yellow cattle breeds were studied for the molecular genetic diversity in MHC-DRB³*exon2 by DNA sequencing. A total of 259 DRB³*exon2 alleles including 131 newly identified ones were found. The number of alleles represents differences in breeds, indicating genetic variations among different breeds. The estimation of the average rate of synonymous（dS）and non-synonymous（dN）substitution in the exon 2 of BoLA-DRB3 showed there was a higher ratio of dN to dS substitutions in the peptide-binding site (PBS) region. The amino acid components of 17 polymorphic sites were significant difference among breeds, including 8 PBS.