To investigate the prognostic value of circulating apolipoprotein AI (apoAI) levels and develop a new prognostic model in individuals with acute-on-chronic liver failure (ACLF) and acute decompensation (AD) of liver cirrhosis caused by hepatitis B virus (HBV) infection.Baseline levels of serum lipids were measured, and data concerning the presence of complications were collected from 561 HBV-ACLF and AD patients. Survival analysis was conducted by log-rank test. Proportional hazards model was used to perform multivariate analysis. The dynamics of serum apoAI levels were also explored in 37 HBV-ACLF patients.In the cohort, the negatively correlation was found between the Model for End-Stage Liver Disease (MELD) score and serum apoAI levels (r = -0.7946, P < 0.001). Circulating apoAI concentration was an independent risk factor for 90-day survival according to Cox multivariate analysis. A new prognostic score-integrated serum lipid profile for ACLF patients (Lip-ACLF score = 0.86×International Normalized Ratio (INR) + 0.0034×total bilirubin (TBIL) (µmol/L) + 0.99× hepatorenal syndrome (HRS) (HRS: no/1; with/2) + 0.50×hepatic encephalopathy (HE) (grade/ponint: no/1; 1-2/2; 3-4/3) - 2.97×apoAI (g/L) + 5.2) was subsequently designed for the derivation cohort. Compared to MELD score, Child-Turcotte-Pugh (CTP) score or apoAI, Lip-ACLFs was superior for the prediction of 90-day outcomes (receiver operating characteristic curve (ROC): 0.930 vs. 0.885, 0.833 or 0.856, all P < 0.01), as was the validation cohort (ROC 0.906 vs. 0.839, 0.857 or 0.837, all P < 0.05). In Kaplan‒Meier survival analysis, low apoAI levels (< 0.42 g/L) at baseline indicated poor prognosis in ACLF and AD patients. Among the 37 patients, the deceased individuals were characterised with significantly decreased serum apoAI levels during the follow-up test compared with those at baseline (P < 0.05), whereas in patients with a good prognosis, the serum apoAI levels remained stable during the follow-up.In HBV-ACLF and AD patients, lower serum apoAI levels suggest greater disease severity and 90-day mortality risk. For predicting the short-term prognosis of these patients, the new Lip-ACLF score might serve as a potential model.© 2025. The Author(s).