Abstract: Mesenchymal stem cells (MSCs), a subset of totipotent stem cells, have the ability of self-renewing, multiple differentiation potential and low immunogenicity. They play an important role in immunoregulation by inhibiting the proliferation of lymphocytes, influencing the differentiation and maturity of dendritic cells and modulating natural killer cells and other inherent immunity cells' activity. MSCs can be isolated from bone marrow, umbilical cord amniotic membrance, fat aspirate and dental pulp. Under specific stimulus, they can differentiate into osteocytes, adipocyte, and chondrocytes in vitro. Recent studies have demonstrated that MSCs can effectively treat rheumatoid arthritis, multiple sclerosis, inflammatory bowel disease, acute lung injury and other inflammatory diseases, which shows a growing promise in the clinical application.