报道７８例多发性肌炎（ＰＭ）／皮肌炎（ＤＭ）肌电图检测。结果，病理性自发电位３３．１％，肌强直样电位６．５％，时限缩短６０．１％，波幅降低６８．０％，多相波增多７０．５％，不正常波型７４．５％，峰值波幅降低７３．０％。各项指标异常在所检部位肌肉分布发现，下肢重于上肢，下肢屈肌重于伸肌。提示选择股二头肌、腓肠肌作肌电图检测（ＥＭＧ），可望提高阳性率。 Report 78 cases of polymyositis (PM) / dermatomyositis (DM) EMG test. The results showed that the pathological spontaneous potential was 33.1%, myotonia-like potential was 6.5%, the time limit was shortened by 60.1%, the amplitude was reduced by 68.0%, the polyphase wave was increased by 70.5% and the abnormal wave pattern was 74.5 %, The peak amplitude decreased 73.0%. Abnormalities in various indicators found in the seized parts of the muscle distribution, lower limbs in the upper limbs, lower limb flexor extensor muscles. Tip selection biceps, gastrocnemius muscle electromyography (EMG), is expected to increase the positive rate.