Liver sinusoid endothelial cells are the first defense mechanism that protects the liver against various injuries,and they also play a significant role in the development of liver fibrosis and liver cirrhosis caused by chronic liver injury.They are involved in liver fibrosis by mediating liver inflammation,participating in sinusoid capillarization and revascularization,activating hepatic stellate cells,secreting many proinflammatory cytokines,participating in extracellular matrix formation,and mediating liver microcirculation disturbance.Clarification of these mechanisms helps to identify new targets and develop new regimens for the treatment of liver fibrosis.