Abstract: he polymorphisms of HSP70-1 gene in 253 Chinese Holstein dairy cows were studied, and the association between the polymorphisms and somatic cell score (SCS) were analyzed. PCR-SSCP, PCR-RFLP and DNA sequencing were used to investigate mutations in the coding region of HSP70-1 gene. The G→A→C mutation at 1 623 bp and G→A mutation at 2 409 bp were found and both of them were silence mutations that caused no alteration in amino acid sequence. Chi-square test showed both loci weren′t at Hardy-Weinberg disequilibrium in Chinese Holstein. In the meanwhile, the association of 2 409 locus and SCS was not significant. However, the polymorphism at 1623 locus affected SCS signifi-cantly (P<0.05). The SCS of genotype CC was significantly lower than that of genotype AG and GG (P<0.05), so genotype CC was mastitis resistant. These results suggest that genotype CC of HSP70-1 gene may be used as a molecular and genetic marker to improve the phenotype of anti-mastitis in Chinese Holstein dairy cows.