Objective　To understand the difference in characteristics between juvenile dermatomyositis (JDM) and adult dermatomyositis (ADM). Methods  Sixty-one cases of JDM were retrospectively analyzed and compared with 30 cases of ADM. Results  The rashes were presented as the initial symptom in all expect one JDM patients. Gottron’s papules were presented in 90% JDM patients and 67% ADM patients. Calcium deposition was presented in 7% JDM patients and none of the ADM patients. The cardiovascular system was involved in 7 % JDM patients and 23% ADM patients. Cancer occurred in none of JDM patients and 13% ADM patients. In JDM and ADM patients, the ratio of elevated muscle enzymes from highest to lowest was LDH, hydroxybutyric acid enzyme, CK-MB, AST, and CK. The positive ratio of magnetic resonance (MRI) all exceeded 80% in JDM and ADM groups. Two cases died in each group. Conclusions  The clinical presentation of JDM is basically the same as that of ADM. The most common initial symptoms in JDM are skin rashes and Gottron's papules. Cardiovascular disease and cancer are less in JDM than in ADM. MRI is valuable in the diagnosis of DM.