The purpose of this study is to analyze the change of blood lipid concentration and leptin hormone, as well as to estimate the correlation between leptin hormone and blood lipid before and after training, which was conducted to the subject of obese adolescents in growth period. The subject of this study is as the male students at D high school in B city， 14 students was selected among the students whose BMI(kg/m²) is more than 25，and they consisted of exercise group (N=7, age: 18,3±0.86) and control group (N=7, age: 18_1±0.52) through random sampling method. Blood component analysis is TG, Total Cholesterol, LDL-C, HDL-C, Leptin, and the results from analysis are as follows. In the change of blood Triglyceride & Total Cholesterol & LDL-C & Leptin followed by 12 week training, exercise group showed very significant difference, compared with control group(p<.001), and in the change of blood HDL-C followed by 12 week training, exercise group showed very significant increase, compared with control group (p<.001). On the result of analyzing the correlation between Leptin hormone and TG, Total Cholesterol, LDL-C, HDL-C before and after 12 week aerobic exercise, the significant correlation did not show. As the above result, through the 60%HRmax aerobic exercise for 50 minutes every three times a week for 12 consecutive weeks, TG, Total Cholesterol, LDL-C, Leptin in blood lipid was decreased and HDL-C was increased. Therefore, we can infer this 60%HRmax ae