The purpose of this study was to investigate the effects of short-term resistance training and detraining on strength and body composition in male adolescents. METHOD Thirty-two boys aged 14 – 16 years were randomly assigned into resistance training (RT) and control groups. RT adopted moderate and low workload (65 ~ 75% maximal muscular strength) to train biceps and quadriceps twice a week for 11 weeks. Control group just had routine physical education (PE) courses. RESULTS It was found that, for male adolescents, 1) 11-week RT did not change the girths of biceps and quadriceps but increased the maximal strength of upper and low limbs while growth had positive effects on the girths and maximal strength, 2) detraining for 11 weeks led to all the changes disappeared, 3) and short term RT and detraining had no significant effects on body composition. CONCLUSION The research reveals that the short-term training can increase the maximal strength of the upper and low limbs in male adolescents. The increases are not caused by muscular development or the changes of body composition, but result from the increase of the neural muscular regulation possibly.