Abstract: To search the molecular markers that are associated with mastitis and to provide theoretical basis for the Holstein cattle breeding and disease resistance， the polymoprhisms of TLR6 gene in 303 Holstein cattle in Ningxia were detected by PCRSSCP technique, and the effect of TLR6 gene c.640G>A locus mutation on somatic cell score(SCS) of milk and various factors was analyzed using general linear model. The results showed that there was a significant relationship between TLR6 gene c.640G>A locus mutation and SCS and parity. The GA and AA genotype had significantly lower SCS than GG genotypes（P<001）. So, GA genotype of c.640G>A locus mutation could be applied as a low SCC / SCS superior genotypes in Chinese Holstein breeding.

Key words: Holstein cattle, TLR6 gene, c.640G>A, somatic cell score