Excessive activation of innate immune response contributes to the pathogenesis of acute-on-chronic hepatitis B liver failure (ACLF-HBV). miR-146a was recently found to be implicated in the regulation of innate immunity. In this study, we explored the biological significance of a single-nucleotide polymorphism (rs2910164) within the miR-146a gene in the risk of acquiring ACLF-HBV. We completed a hospital-based case-control study including 717 cases of HBV-infected patients-251 cases of ACLF-HBV and 466 cases of chronic hepatitis B. Whole blood samples were collected for isolation of DNA and peripheral blood mononuclear cells (PBMCs). The association between genotypes and risk of ACLF-HBV was analyzed by multivariate unconditional logistic regression, with adjustment for sex and age. Our results showed that the GG homozygote was a protective genotype in terms of susceptibility to ACLF-HBV, with odds ratio = 0.496, 95 % confidence interval = 0.309-0.797, P = 0.004 compared with CC+GC genotypes. The amount of mature miR-146a in PBMCs was significantly higher in the GG homozygote group than those in the CC and CG genotype groups of ACLF-HBV patients. The GG genotype group also represented lower serum level of TNF-alpha and higher survival rate (follow-up period = 4 months). In conclusion, The GG genotype within the pre-miR-146a is reversely associated with susceptibility of ACLF-HBV in the studied Chinese population. This may be partially explained by the relatively higher amount of mature miR-146a and the lower serum level of TNF-alpha in this genotype group.