Regulatory B cells (Bregs) are a subset of B cells with immunomodulatory effects. The study of Bregs began with a variety of animal models of immune diseases. Studies in patients with autoimmune diseases have further clarified that Bregs are a group of immune cells that secrete inhibitory cytokines such as interleukin-10. Abnormal functions and numbers of Bregs have been found in a variety of autoimmune diseases. The study of the negative immune regulatory network involving Bregs is expected to provide new therapeutic ideas for diseases such as immune diseases, cancer, infection and inflammation. Starting from the discovery and immune regulation mechanism of Bregs, this paper focuses on its regulatory mechanism and clinical research value in the occurrence and development of autoimmune diseases, tumors, infectious diseases and inflammation.