Abstract: Based on the primer sequences of two SNPs (AJ237937 and AF079568) of STAT5A gene from the GenBank database, polymorphisms on the two SNPs were detected in 758 Chinese Holstein cattles with PCR-SSCP and association between the polymorphisms and 5 milk production traits were analyzed. We found that the SNP1 was A/G (9501) and the SNP2 were T/C (12440) and CCT insert/delete (12550). Statistical results indicated that the SNP1 was significantly associated protein percentage (p<0.05), the SNP2 was significantly associated with milk yield (p<0.01)，fat yield (p<0.05) and protein yield (p<0.05), and the diplotype was associated with milk yield (p<0.01), protein yield (p<0.01) and fat yield (p<0.05). Duncan’s multiple-range test showed that the cows with genotype AB of SNP2 had significantly higher milk yield (p<0.01)，fat yield (p<0.05) and protein yield (p<0.05) than the cows with genotype AA. In addition, the least square mean for milk yield, fat yield, and protein yield of diplotype H1H2 was significantly higher than those of other four diplotypes (p<0.05 or p<0.01), respectively, and the least square mean for milk yield and protein yield of diplotype H3H4 was significantly higher than those of other four diplotypes (p<0.01). Our finding implied that STAT5A gene would be useful candidate gene in selection program on milk production traits in Holstein Cattle.