This study focuses on elementary school swimming club students to observe their physical fitness developments for six months. In this study, there was one physical fitness check in the beginning of the semester and the second physical fitness check was performed after six months of training, and comparison the differences of two physical fitness check. Research purposes described as following: 1. To understand the students' raw scores and percentile rankings of sit-bend, 60 seconds sit-ups, 800-meter run-away, standing-long-jump pre-test and post-test. 2. To understand the relationship between the frequencies of students' participation of physical fitness and the progress. 3. To understand the relationship of the frequencies of students' participation and performances in post-test. After six months of group activities, subjects' performance in sit-bend, 60 seconds sit-ups, 800-meter run-away and standing-long-jump improved. Data was analyzed by paired sample t test and Pearson correlation. There was no significant difference between the pre- and post-tests of sit-bend. There were significant differences between the pre- and post-tests of 60 seconds sit-ups, 800-meter run-away and standing-long-jump. There was no correlation between subjects' participation times and improvements. There was no correlation between subjects' participation times and performances in sit-bend, however, there were medium and high correlations in 60 seconds sit-ups, 800-meter run-away and standing-long-jump. There was a moderate negative correlation of subjects' participation and swimming time. The subjects' swimming time and performance on 60 second sit-ups was moderate negative correlation. We suggest that diet control and exercise are both important for better health. Back softness training need to be emphasized.