We observed the changes of quadriceps femoris EMG before and after treatment on treatment 41 cases of poliomyelitis sequelae with series electroacupuncture. In 41 patients muscles strength of quadriceps femoris before treatment in 35 cases was below 0 degree and 1 degree. The changes of EMG, Most had no motor unit potential, some only a few but duration was long, and amplitude decreased markedly. A few had fibrillation or positive sharp wave. The changes in EMG accorded with the diagnosis of poliomyelitis sequelae. After 3 month treatment, tee EMG findings were decreasing or there was loss of fibrillation, appearance of motor unit potentials, increase of the amount of motor unit potentials, prolongation of duration and increasing of amplitude of motor unit potentials, appearance of polyphasic potentials etc. Through analysis of EMG, 32 among 41 cases were improved, effective rate was 78%, P less than 0.01. EMG indices indicate the efficacy of series mg electroacupuncture in treating the sequelae of poliomyelitis and confirm the clinical therapeutic effect of the treatment. The indices indicate that the pathological changes of damaged anterior horn cells of the spinal cord were decreased and partial recovery of nervous function. The EMG changes paralleled those in clinical therapeutic effect of treatment and changes of muscle strength.