The purpose of this study is to determine the effect of 12 weeks of circuit training of experimental group and control group. Both groups have 9 members and the experimental group has been trained for 12 weeks through circuit training. The results of this study are as follows ; Through pre and post tests, the control group didn`t show significant differences in every measuring item, but the experimental group revealed statistically significant difference in HR peak, VO_2 pdeak, Ve peak, R, body fat(subscapular, triceps, chest, abdominal) except VO_2 peak/kg. The long-term training over one year is more required to compare the effectiveness of the training and the physical fitnessn with nonretarded persons than the short-term training. Furthermore, future studies should look into more appropriate measurements and programs for persons with mental retadation.