The purpose of this study was to analyze the effect of swimming exercise on body fat. physical fitness and blood lipids of obesity elemenraty. Subjects divided into three group : week-3times group(10). week - 5time group(10). control group(10). Age range of subject is 11-12 yrs. Each group were swimming exervise during 8-weeks and during precriptive duration measured the each variations. The conclusion of the study was as follows: 1. Body fat during prescription duration exercise showed significant (p<.0421) differences at 3-times and 6 times group according to exercise frequence and difference among each group after 8-weeks showed not significant at each group 2. Physical fitness dufing prescription duration of 3-times and 6-times group according to exercise frequence showed significant(p<.0001) differences at back strength, stand long jump , whole body reaction time and difference among each group after 12- weeks showed not significant at each group. \' 3. In the serum lipids during prescription duration of 3-time and 6-time group according to exercise frequence, T.C, T.G, HDL-C and T.C/HDL-C ratio showed significant (p<.0001, p<.0001 p<.0001, p<.0031) differences at during 12-week exercise and difference among each group after 12-weeks, T.G and T.C/HDL-C ratio showed significant (p<.0310) at 3- time and 6-time group. From results of this study , regular swimming according to exercise frequence fegad to effect of body fat and physical fitness factors, espescally lipids showed imcresed to changed level at 3-time than 6 time with high exercise frequence, therefore in the future. frequence and intensity of siwimming exercise will selected application