B-1 cells are a class of atypical B lymphocytes distinguished from conventional B-2 cells. It has been reported that the B-1 cells may play some roles in innate immunity, autoimmune diseases, and leukemia. Since B-1 cells are one of the most important sources of IL-10, we hypothesize that the B-1 cells may suppress the T cells activity and induce the generation of Tr1 cells. The mouse peritoneal cavity cells were analyzed and the B-1 cells were purified for following experiments. These B-1 cells could spontaneously secreted IL-10 and up-regulated the IL-10 production after LPS stimulation. The B-1 cells would inhibit proliferation of T cells through soluble factors. However, the B-1 cells could not efficiently induce the generation of IL-10-producing Treg cells in our system. In the contrast, the B-2 cell-induced Treg cells, “TofB2” cells, showed suppressive ability, and they presented Foxp3-CD25+CD62L+ phenotype and expressed high level of IL-10 and IL-4. In conclusion, the B-1 cells inhibited proliferation of T cells through soluble factors, and the B-2 cells join the immune modulation through inducing Treg cells generation. In different mechanisms, both B cell populations play regulatory roles in immune response. The studies may provide potent clinical application in treatments for autoimmune diseases.