Dermatomyositis can be diagnosed by general examination, serum myosin profile, autoantibodies, electromyography, muscle biopsy and other tests. 1. General examination: blood routine can see increased leukocytes, accelerated blood sedimentation, increased blood creatine, decreased creatinine, increased serum myoglobin, increased urinary creatine excretion. 2. Serum muscle enzyme spectrum: creatine kinase, aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase are increased. 3. Autoantibodies: most patients are positive for antinuclear antibody, some patients are positive for rheumatoid factor, and positive anti-Jo-1 antibody, anti-SRP antibody and anti-Mi-2 antibody are also significant for the diagnosis of dermatomyositis. 4. Electromyography: Electromyography in patients with dermatomyositis can detect myogenic lesions at an early stage. 5. Muscle biopsy: muscle biopsy is important in the diagnosis of this disease. It is recommended that patients with dermatomyositis go to the hospital in time for consultation and treatment under the guidance of doctors.