Background　B cells are typically characterized by the ability to produce antibodies and cytokines， also possess the ability to present agents. Regulatory B cells， as the B cell functionally distinct subset， performing both pathogenic and regulatory role in several murine models of autoimmunity and inflammation.　Objective　To discuss the most recently progress in the role of regulatory B cells.　Content　This paper sums up the characters of regulatory B cells， and the functions of regulatory B cells in the autoimmune diseases and tumor.　Trend　Currently， the exact identity and origin of the regulatory B cells remains elusive. The complex cellular network may differ for each pathology. Control of regulatory activity would be an alternative therapy for autoimmune diseases and tumors.