This study was performed to analyze the psychologic change of Tae-kwon-do Athletes who were wearing the mouth guard and one of contact sports during their matches of Tae-kwon-do 10 selected Tae-kwon-do athletes who had no injuries which they had college Tae-kwon-do sparring matches in the Cheon-an area have participated in the study. The oral impressions if the selected athletes were taken to produce for individual custom mouth guards. After the mouth guards were produced, each of them sat in a chair and attached G.S.R. surface electrodes in the palms of the ends of the second and third fingers of their left hands without moving their left hands, And then they were asked to watch footages of Tae-kwon-do games to stimulate them as if the had have a mock match, and Labscribe2 which are one of polygraphy was used to record their G.S.R. values. To determine whether the mouth guards affected the changes of their psychological status during the sparring matches of not, the experimental group wore the mouth guards while they watched the footages, and the control group didn’t wear any mouth guards. The G.S.R. values of the two groups were measured while the watched the footages. To see if there were and significant polygraphy differences between the experimental group and the control group in G.S.R. values, a statistical package SPSS was used to make a comparative analysis. And there were significant change in between the experimental and control group that wore the mouth guards, and it was concluded the wearing mouth guards exerts an influence on change in the psychological state of Tae-kwon-do athletes while they watch a footage of mock match.