The purpose of the study was to examine the difference of the Physical fitness grade of elementary school girls to their heart function in a bid to let them wake up to the importance of their health status and the necessity of exercise. And it\'s also intended to lay the foundation for improving school Physical education activities. The subjects in this study were 16 students who were selected by random sampling from among girls in their sixth year of J elementary school located in the city of Incheon. Out of them, eight female children ranked hight Physical fitness, and the others were rated low. In the first phase of the study, the participants were exposed to physical examination. For the comparison of wave pattern, ST segment slope was also utilized, which shows myocardium hypertrophy, while the subjects exercised using Modified Kiss(re) Protocol. The collected data were analyzed with SPSS 12.0 program, and Mann-Whitney U Signed Ranks Test was employed, which was a nonparametric test. The level of significance was set at p<.05. The findings of the study were as follows: There was significant mean rank difference in R-R, P-R. However, no significant mean rank difference was found in QRS duration. Hight physical fitness grade electrocardiogram\'s amplitudes and ST segments slope had no significant mean rank difference, hight grade showed more adaptations to exercise, which meant left ventricle myocardium hypertrophy cant in stage 5. ※ Keywords: physical fitness grade, electro