〔Abstract〕 Objective To investigate the expression level of Interleukin-26(IL-26) in hepatitis B virus-associated acute-on-chronic liver failure(HBV-ACLF) and its clinical significance.Methods Serum IL-26 levels were measured by enzyme-linked immunosorbent assay(ELISA) in 53 patients with HBV-ACLF, 53 patients with chronic hepatitis B(CHB) and 18 healthy controls. General data were statistically analyzed, and relevant clinical indicators were analyzed for their correlations with IL-26. Multivariate logistic regression analysis was used to assess independent risk factors for prognosis of patients. ROC curve and survival curve were used to evaluate the prognosis performance of patients. Results The level of IL-26 in HBV-ACLF patients was significantly higher than that in non-aclf patients. The expression of IL-26 was positively correlated with creatinine( CREA) and activated partial thromboplastin time( APTT). Multivariate logistic analysis showed that total bilirubin( TBIL) and IL-26 were independent risk factors. The prognostic model AUC( 0. 933) established by IL-26 combined with MELD was more sensitive and accurate than single index. Serum IL-26>1 019. 68 pg/ml had reliable prognostic accuracy in predicting 90-day mortality in patients with HBV-ACLF. Conclusion The level of IL-26 significantly increased in patients with HBVACLF,which has important clinical significance and application value in monitoring the condition and prognosis of patients with HBV-ACLF.