The purpose of this study was to investigate the effect of swimming class on body composition in university students. Sixty students with mean age of 20.95±1.23 yrs; height 167.03±7.72cm; weight 60.95±9.07kg (32 males, 28 females) attended swimming class, once a week, 90 minutes per class for 12 consecutive weeks. They were tested before and after the training in body composition by the body composition analyzer (in body 3.0). The body composition test included weight, soft lean mass, lean body mass, body fat mass, percent body fat, WHR. The data was processed by SPSS for windows 10.0 software system and the t-test was used to analyze the comparison of before and after training in all tested subjects. The significant level was set at α=.05. The results were as followed: 1. The male and the female samples reached significant level in weight, soft lean mass, lean body mass, body fat mass, percent body fat, and WHR; except male samples had no significant difference in soft lean mass and lean body mass. 2. The female samples gained one-time more than male samples did in soft lean mass and lean body mass. 3. The male and the female samples improved significantly in upper muscular strength and trunk strength while there was no significant improvement and difference in lower muscular strength. We concluded that the 12 weeks swimming class actually improve the body composition percentage of students.