The gastrointestinal tract is an extremely complex ecosystem,and a healthy and intact intestinal mucosal barrier is the basic defense against the translocation of harmful substances.The impaired function of the intestinal barrier in acute-on-chronic liver failure(ACLF)is further aggravated by the dysregulation of intestinal microecology,which leads to bacterial translocation and endotoxemia.Maintaining the normal function of the intestinal mucosal barrier is important for the treatment of ACLF.This paper reviews the function of the normal intestinal mucosal barrier,the relationship between the damaged intestinal barrier and ACLF,and the impact of the damaged intestinal barrier on ACLF progression.