〔Abstract〕 Objective To investigate the diagnostic endoplasmic reticulum aminopeptidase-1(ERAP1) in patients with hepatocellular carcinomae(HCC). Methods Enzyme-linked immunosorbent assay(ELISA) was used to detect the serum levels of ERAP1 in HCCpatients, cirrhosis patients and healthy controls(HC).Multivariate logistic regression was used to analyze the independent risk factors of the severity and prognosis, and receiver operating characteristic curve(ROC) was used to evaluatesensitivity and specificity of ERAP1 in the diagnosis of different degree of disease and prognosis. Results The serum ERAP1 level of HCC was related to tumor stage, tumor size and number of cancer focal(P<0.05). ERAP1 level of HCC patients was positivecorrelated with ALT, AST, TBIL and AFP, while negative correlated with ALB(P<0.05). ERAP1 was found to be an independent predictor of different severity and prognosis. When joint diagnosing HCC with AFP, the area under the curve(AUC) was 0.932. For the diagnosis of poor prognosis, the AUC was 0.742. Conclusion Serum ERAP1 level has important clinical significance and potential application value in evaluating the severity and prognosis of HCC patients.