Liver failure (LF) is a dramatic clinical syndrome with massive necrosis of liver cells. and liver transplantation is the only available therapeutic option for patients suffering with this condition. However, lack of donors, surgical complications, rejection, and high cost are serious problems. Previous study showed that bone marrow derived mesenchymal stem cells (BM-MSCs) replace hepatocytes in injured liver, and effectively rescue experimental liver failure and contribute to liver regeneration. In this study, the patients with LF will undergo administration of human umbilical cord mesenchymal stem cells (UC-MSCs) via peripheral vein transfusion to evaluate the safty and efficacy of UC-MSCs treatment for these patients.