Side population cells have high tumorigenicity, self-renewal, and multi-directional differentiation potential, as well as chemotherapy resistance. All these characterristics of side population cells are similar to that of the tumor stem cells, so the side population cells gradually have become the point of penetration for the study of tumor stem cells, thus to lay a foundation to further explore the biological function and molecular mechanism of tumor stem cells. The patients with multiple myeloma and almost all MM cell lines were detected in the side population cells. The tumorigenicity, cell cycle, differentiation potential, surface markers and drug resistance of side population cells were studied by cell sorting with flow cytometry. The pathogenesis of multiple myeloma, and application to clinical diagnosis at the early stage all were understood deeply, so as to provide new ideas for further research on treatment. In this review, the research progress of side population cells in multiple myeloma is briefly summarized.