Abstract: Liver fibrosis is characterized by scarring of liver tissue, which is an intermediate pathological process of chronic liver disease developing into liver cancer. Its mechanism involves multiple signal pathways, and its reversibility is a current research hotspot. Bone marrow mesenchymal stem cells (BMSCs) are adult stem cells with multi-differentiation potential. They have ability to differentiate into liver-like cells in vivo and in vitro to perform normal liver cell functions. Modern pharmacological experimental studies have shown that the use of BMSCs alone or in combination with active factors, Chinese medicine or Chinese medicine monomers, genetic modification and other methods can promote their proliferation, differentiation, and migration, improve the therapeutic effect, and play a role in improving liver fibrosis. By summarizing the existing literature, the therapeutic mechanism of BMSCs in improving liver fibrosis is reviewed from the aspects of the pathogenesis of liver fibrosis, the improvement mechanism of liver fibrosis, the biological characteristics of BMSCs and its improvement mechanism, so as to provide reference for the later development of BMSCs cell therapy.