Abstract: Objective：To study the ratio alteration of regulatory T cells (Treg cells) and helper T cells 17 (Thl7 cells) in peripheral blood (PB) and bone marrow (BM) in patients with multiple myeloma (MM), the related transcription factors (e.g. Foxp3, RORγt) mRNA expression, and the clinical significance of Treg/Thl7 balance. Methods：Fourty- six MM patients were enrolled, including 20 newly diagnosed patients, 16 patients at the plateau stage, and 10 relapsed/refractory patients. The control group was consisted of 20 healthy people undergoing a medical examination. The number of Treg and Th17 cells in PB and BM was determined by flow cytometry analysis. The Foxp3 and RORγt mRNA expression levels were tested by RT- PCR. Serum C- reaction protein (CRP) and interleukin 6 (IL-6) levels were tested with routine lab methods. Results：Treg cells’ percentages in PB and BM in newly diagnosed group and relapsed/refractory group were significantly higher than those in normal control group and plateau group (P<0.05). There was no significant difference in Th17 cell percentage in PB or BM in newly diagnosed group and relapsed/refractory group comparing with that in the normal control group and plateau group. The Treg/Th17 ratio in either PB or BM was higher in newly diagnosed group and relapsed/refractory group compared with that in the normal control group and plateau group (P<0.05). The changes of the transcription factors (Foxp3 and RORγt) mRNA in PB and BM of MM patients were consistent with the results of Treg/Thl7 ratio. The changes of serum CRP and IL- 6 levels were consistent with the Treg/Th17 ratio in MM patients. Conclusions：The balance of Treg/Th17 in PB and BM of MM patients inclined to Treg during active period, and the expression of Foxp3 level increased. The levels of IL- 6 and CRP in serum are consistent with the change trend of Treg/Th17 ratio, which could be used to predict the prognosis of MM patients.