Objective The objective of this study was to investigate the relationship between CYP2D6 gene polymorphisms and the concentrations of tamoxifen metabolites in breast cancer patients. Methods Peripheral blood samples from breast cancer pa-tients were collected to detect the single nucleotide polymorphism(SNP)of s16947,rs1065852 and rs28371725 gene sites on CYP2D6 gene from January 2010 to December 2012. Genotypes of the three SNPs of CYP2D6 and the concentrations of tamoxifen metabolites were detected in breast cancer patients. Statistical analysis was performed using an independent sample Kruskal-Wallis test in a non-parametric test. Results There was a statistical difference in the concentrations of tamoxifen metabolites 4-OH-N-D-TAM and 4′OH-N -D -TAM in the blood in different CYP2D6 gene genotype carriers at rs16947 site ( P =0. 049), indicating that the rs16947 site of CYP2D6 gene affected the metabolism of tamoxifen drug in breast cancer patients. Conclusion The genotype of CYP2D6 gene at rs16947 site is related to the blood concentration of tamoxifen metabolites in breast cancer patients.