The aim of this investigation was to study the EMG of masseter of edentulous patients in chewing cycle. 18 subjects were examined by Disa-2000M Neuro-electromyograph. It was found that the period of chewing cycle of the patients with complete denture was distinctly longer than that of normal people, and the change of the duration prolongs the time phases. The velocity was relatively slow when trying to keep the stability of dentures. The amplitude of potential in masseter was lower in chewing cycle, but it did not affect the function of mastication. The abnormal pause after occlusal contact of denture had an influence on the function of mastication.