Objective: To screen serum protein markers and evaluate their diagnostic application value in hepatitis B-related acute-on-chronic liver failure (HBV-ACLF). Methods: Serum samples of patients with HBV-ACLF, chronic hepatitis B (CHB) and normal healthy volunteers (n = 5/group) were determined by cytokine antibody chip in line with the Chinese Diagnostic Standards Study for HBV-ACLF (COSSH-ACLF) cohort. The differentially expressed proteins significance were identified by microarray analysis and prediction. The preliminary serological markers of HBV-ACLF were screened for diagnosis. The potential markers were determined by enzyme-linked immunosorbent assay (ELISA), area under the receiver operating characteristic curve (AUROC) analysis and liver tissue immunohistochemistry for the diagnosis of HBV-ACLF. Student t-test or Mann-Whitney U test were used to compare the continuous measurement data between the two groups, and analysis of variance and Kruskal-Wallis test were used to compare the continuous measurement data between multiple groups. Results: Cytokine antibody chip preliminary screening results showed that the expression levels of these six cytokines, namely, macrophage inflammatory protein 3α (MIP-3α), hepatocyte growth factor, E-selectin, osteopontin, growth differentiation factor 15 and carcinoembryonic antigen-related cellular adhesion molecule 1 were significantly increased in the HBV-ACLF group. Among them, the expression level of MIP-3α was significantly higher in the HBV-ACLF group (99.6 times higher than CHB group and 146.9 times higher than healthy volunteers' group, respectively, P < 0.0001) as validated by serum ELISA in 132 HBV-ACLF cases, 91 CHB cases and 72 healthy volunteers. AUROC analysis showed that the high expression of MIP-3α could be used as a marker to distinguish patients with HBV-ACLF from CHB. The AUROC was 0.995 (95% CI: 0.990 ~ 1.000), with sensitivity and specificity of 95.5% and. 98.9%, respectively. Immunohistochemistry showed that MIP-3α was positively expressed in HBV-ACLF-derived liver tissues, and negatively expressed in CHB-derived liver and normal liver tissues. Conclusion: Serum MIP-3α level is closely related to the pathological characteristics of HBV-ACLF. Therefore, it may be used as a potential serological marker for the diagnosis of HBV-ACLF.