Objective To establish a rat model of acute-on-chronic liver failure (ACLF). Methods On the basis of immune liver fibrosis induced by bovine serum albumin (BSA), the rat model was established by intraperitoneal injection of D-galactosamine and lipopolysaccharide. Histopathology of the liver and intestinal mucosa as well as the ultrastructure of intestinal mucosa were used to judge whether the rat model of ACLF was established successfully. Results Eighty-eight percent of the rats produced BSA antibodies after subcutaneous injection of a BSA emulsion within 34 days. After further injections of the BSA emulsion via the tail vein for 6 weeks, liver histopathology revealed obvious liver fibrosis. The rat model was established by intraperitoneal injection of 100 μg / kg lipopolysaccharide ( LPS) and 200 mg / kg D- galactosamine. The liver and intestinal mucosa were examined by hematoxylin-eosin staining and ultrastructural analysis by transmission electron microscopy. The result were consistent with the pathological characteristics of ACLF. Conclusions One intraperitoneal injection of D-galactosamine combined with LPS successfully establishes a rat model of ACLF with a high modeling rate and low mortality, which can be used for further study.