Objective: To explore and confirm feasibility the T2 maps and readout-segmented echoplanar imaging (rs-EPI) diffusion-weighted imaging (DWI) characteristics of the thigh muscles for dermatomyositis (DM) patients. Methods: This study was approved by the University Institutional Review and written informed consent was obtained from all subjects before enrollment (trial registration number: TJ-C20121221). 28 patients with DM proven by diagnostic criteria were enrolled in the study along with 9 healthy control subjects. Conventional MR, T2 maps and rs-EPI DWI were obtained for all subjects. Both of T2 and apparent diffusion coefficient (ADC) values for thigh muscles were compared between the DM and healthy control groups. The amount of inflammation and fatty infiltration were respectively assigned a score of 0 to 5 for all thigh muscles. The Kruskal-Wallis tests were utilized and the Spearman correlation coefficients models were used to correlate both of the T2 and ADC value with non-quantitative MRI. P-values <0.05 reflected statistical significance. Results: Both of the T-2 and ADC values among all affected muscles, unaffected muscles and the control groups were respectively statistical difference (p < 0.05 respectively), the T-2 value of affected muscles was greater than that of unaffected muscles in DM patients (p < 0.05). Differences of the T-2 value in DM patients among the combination the edematous with fatty infiltration score groups were statistically significant (p < 0.001). The T-2 value showed a significant correlation with the non-quantitative MRI score for edema and fatty infiltration. Conclusions: T-2 maps may have a specialized ability for the detection severity of damaged muscles in comparison to the rs-EPI DWI sequence. Advances in knowledge: A new application of rs-EPI DWI is proposed for DM patients. First, comparison of T-2 maps and rs-EPI DWI technology are applied for DM. The results demonstrate that T-2 maps may be more potential value in determining the severity of diseased muscles for DM patients.