Abstract: Hepatitis B-induced acute on chronic liver failure（HB-ACLF） is mainly due to the immune-mediated liver injury. More and more studies have found that regulatory T （Treg） cells and T helper cell 17 （Th17） play important roles in the immunopathogenesis of HB-ACLF. Treg and Th17 originate from the same initial CD4+T cells，but restrict each other in differentiation and functions. Studies have indicated that the imbalance of Treg/Th17 ratio is closely related to the occurrence and development of ACLF. This article reviews the role of Treg/Th17 in the pathogenesis of ACLF，and provides materials in the study of immunological field of liver failure.

Key words: Acute-on-chronic liver failure, T helper cell 17, Regulatory T cell, Pathogenesis