Objective To investigate the effect of interleukin (IL)-6 rsl800796 locus single nucleotide polymorphisms (SNPs) in the donors and recipients on concentration/dose (C/D) ratios of tacrolimus after liver transplantation.Methods A total of 79 liver transplantation patients whose whole blood concentrations of tacrolimus were determined by using enzyme-linked immunosorbent assay kits were enrolled in the study.Additionally,tacrolimus dosage and trough blood concentration of them was recorded and studied at four weeks after liver transplantation.The SNPs at IL-6 rs1800796 locus were genotyped in both donors and recipients.Then we compared the influence of the different genotypes at this locus on FK506 C/D value for patients.Fluorescent quantitative polymerase chain reaction (FQ-PCR) and immunohistochemical methods were used to test the IL-6 expression levels of mRNA and protein.Results Only donor IL-6 rs1800796 SNPs was associated with tacrolimus C/D ratios at week 2 and 3 after liver transplantation (P ＜ 0.05).While this phenomenon was not finded in recipients from week 1 to 4.The △Ct value in the fast metabolism group contained carriers of genotype CC is (6.6 ± 1.2),while in the slow metabolism group clustered carriers of genotype CG/GG is (7.7 ± 1.1).The difference was significant (P ＜ 0.05).The intermediate expression rate of IL-6 protein in fast metabolism group [80.0％ (24/30)] was higher than that in slow metabolism group [48.4％ (15/31)].There was significant difference (P ＜ 0.05).Conclusion Donor IL-6 rs1800796 SNPs were closely associated with tacrolimus C/D ratios in the early stage after liver transplantation.