The purpose of this study was to contribute to the effective rehabilitation and treatment of the mentally retarded people by finding the close relationship between body organs development and adaptive behavior development. To accomplish the purpose of this study, 32 of mentally retarded persons were selected and divided into three groups, swimming training group(n=11), basketball-training group(n=6), and control group(n=15) for 12 weeks` training. The changes of endocrinologist system and the level of adaptive behavior of subjects were measured before and after the training. In summary, as the result of 12-week training of mentally retarded persons, fitness of them was improved, the changes of whole·simple body reaction time and the endocrinologist responses positively reformed and social adaptability was greatly improved. Considering of the above positive effects, exercise therapy for mentally retarded persons was very effective in improving their physical fitness, leading to mental rest and increasing social ability, so it could be considered as one of effective ways for the rehabilitation and treatment of the mentally retarded.