OBJECTIVE To repopulate the liver of mice with acute liver injury and to make mouse models with chimeric liver by using human umbilical cord blood (hUCB)-derived mononuclear cells. METHODS Fifteen acute liver injury mouse models were induced by carbon tetrachloride intraperitoneal injection followed by two-thirds hepatectomy and all mice were divided into three groups: cell transplantation group (n = 7), negative control group (n = 3) and blank control group (n = 5). HUCB cell preparations were transplanted into mouse spleens of cell transplantation group and phosphate bufferd saline (PBS) was injected into spleens of negative controls. Neither cell suspension nor PBS was given to the blank controls. Pathological changes were observed 7, 14 and 21 days after cell transplantation. Human albumin (ALB) and cytokeratin 19 (CK19) were also detected in the mouse sera and liver tissues. RESULTS All mice showed histological features of acute liver injury. Positive expression of human ALB and CK19 were observed in liver tissues of cell transplantation group 7, 14 and 21 days after cell transplantation. Human ALB could be detected from the sera and liver homogenates of cell-transplanted mice. No positive expression of human ALB and CK19 were observed in liver tissues and no human ALB was detected in sera of negative control group. CONCLUSIONS HUCB-derived mononuclear cells can differentiate into functional human hepatocytes and biliary cells in large quantity in mouse models with acute liver injury, thus a great progress were made in establishing mouse models with chimeric liver.