Purpoes: The study was done to investigate the effects of an exercise program on body composition, cardiopulmonary function and physical fitness in obese children. Methods: Thirty nine children in grades 4, 5, and 6 in elementary school were employed: experimental group(20) and control group(19). The subjects in the experimental group participated in an exercise program for 8weeks, thirty five minutes per session, four times per week. This data was analyzed by ANCOVA and paired t-test. Result: The Height(F=2.615, p=0.027) of the experimental group was significantly different from the control group. Also, in the experimental group, there were significant differences of height(t=4 79, p=0.000), cardiac rate(t=-6.461, p=0.000), body mass index(t=-2.13 p=0.046), muscle strength(t=3.48, p=0.003), and muscle endurance(t=3.20, p=0.005). Otherwise, in the control group, there were significant differences of weight(t=2.27, p=0.036), waist-hip ratio(t=3.16, p=0.005), and muscle endurance(t=-2.38, p=0.030). Conclusion: Jumping rope improved the body composition, cardiopulmonary function, and physical fitness for obese children.