Objective To understand the clinical characteristics of fasting glucose in patients with acute-on-chronic liver failure（ACLF）,and to analyze the risk factors of fasting hypoglycemia,to provide reference values that can help with the early clinical recognition and prevention of hypoglycemia. Methods The clinical data of 931 patients with ACLF hospitalized from May 2013 to December 2019 in the department of infectious diseases of a tertiary hospital in Guangzhou city,were retrospectively analyzed. ACLF patients were divided into hypoglycemic and non-hypoglycemic groups according to the fasting blood glucose levels. The demographics,clinical characteristics,comorbidities and laboratory indicators of patients in the 2 groups were compared,and the risk factors of hypoglycemia were obtained by Logistic regression analysis. Results There were 399 cases（42.86%） of hypoglycemia,including 207 cases（51.88%） of mild hypoglycemia. Binary Logistic regression analysis showed that the length of hospital stay（OR=1.008）,prothrombin time（OR=1.022） and cirrhosis（OR=1.745） were independent risk factors for hypoglycemia in patients with ACLF. Conclusion ACLF patients have a high incidence of mild hypoglycemia,longer hospital stays,longer prothrombin time,and cirrhosis which increase the risk of hypoglycemia. During clinical practice,more emphasis should be placed on screening high-risk patients via early assessment of their hypoglycemic risk,and hence provide timely interventions to reduce the occurrence of hypoglycemia.