Abstract: Objective: To measure the electromyograph (EMG) activities of masticatory muscles in different occlusal patterns by electromyography. Methods: Thirty-three volunteers from Dalian Medical University were divided into four groups: normal control group (n=10), Angle's classⅠmalocclusion group (n=10), Angle's class Ⅱ malocclusion group (n=8) and Angle's class Ⅲ malocclusion group (n=5). Electromyograph was used to measure the EMG activities of masticatory muscles in different occlusal patterns and the data were analyzed by SPSS. Results: In rest position, EMG activities had no significant difference among the four groups. However, during jaw clenching, EMG activity in the masseter of Angle's class Ⅲ malocclusion group was significantly different from those of other three groups. In swallow condition, both EMG activities in the masseter of Angle's class Ⅱ and Ⅲ malocclusion groups were different from that of normal control group. EMG activity in the digastric muscle of Angle's class Ⅲ group was also different from those of other three groups. There were both correlation and differences in the EMG activities of two sides of the masticatory muscles between different occlusal patterns. Conclusion: EMG activities of masticatory muscles between different occlusal patterns were different. Malocclusion may influence the normal function of masticatory muscles.