The purpose of this study was to explore the relationship between lip sealing and lip power, and the effect of button pull exercise on lip posture and lip power. 91 patients who had barely acquired lip sealing had received button pull exercise. They were evaluated for lip power and lip seal before and after Oral Myofunctional treatment. In spite of contrary postures of lip between the Button Pull Group and the Non-Button Pull Group no significant difference for lip strength was found at the first examination. The lip strength of the Button Pull Group had increased twice as much after a half year and decreased thereafter. 25% of the Button Pull Group acquired complete lip sealing after the treatment, 41% did incompletely and 31% did not change.