Objective To explore the changes and clinical significance of regulatory T cell/T help cell 17 (Th17) in the peripheral blood from patients with dermatomyositis (DM).Methods Thirty-six patients with DM were recruited and thirty-six healthy individuals were enrolled as normal controls.The percentage of regulatory T cell/Th17 cell was assessed by flow cytometry and the mRNA levels of Foxp3/RORγt were detected by real-time quantitative reverse wanscription polymerase chain reaction (RT-PCR).The plasma levels of TGF-β1/IL-17 were measured by enzyme linked immunosorbent assay (ELISA).T-test was used for statistical analysis and Pearson's linear analysis were used for correlation analysis.Results The percentage of CD4+ Foxp3+ T cell,the mRNA expression of Foxp3 and the plasma levels of TGF-β1 decreased significantly in patients with DM than in normal controls [(7.2±2.3)％ vs (9.1±3.2)％,(0.44±0.19) vs (0.62±0.25),(37 400±4814) pg/ml vs (41 200±6348) pg/ml,P＜0.05].The percentage of Th17 cell,the mRNA expression of RORγt and the plasma levels of IL-17 increased in patients with DM compared with normal controls [(1.22±0.41)％ vs (0.83±0.14)％,(0.85±0.34) vs (0.61±0.21),(77±32) pg/ml vs (58±20) pg/ml,P＜0.05].There was negative correlation between the percentage of regulatory T cell,the mRNA levels of Foxp3,the plasma levels of TGF-β1 and the serum levels of CK in patients with DM (r=-0.573,-0.593,-0.618,P＜0.05).There was positive correhtion between the percentage of Thl7 cell,the mRNA levels of RORγt,the plasma levels of IL-17 and the serum levels of CK in patients with DM (r=0.582,0.609,0.623,P＜0.05).Conclusion The imbalance of regulatory T cell/Th17 cell may exist in the peripheral blood of patients with DM.Regulatory T cell/Th17 cell may be associated with the pathology of DM.