Physiological fitness and motor performance is different in variable age range, but it has not determined the differences physical adaptation in Children, adults and youth. According to this idea, the purpose of present study is a randomized trial to compare the Effect of age on physical adaptation to fitness training from childhood to boys.96 participants voluntarily were randomized at three ranges of age included: 8 to 10 age group: 12 to 14 age group: 17 to 19 age group training divided into two groups of experimental and control in each age group. Mean± SD of age, height and weight of children was 8.83 ± 0.5year, 1.3+0.1 meter, 34.1+2.8 kg and adolescent 12.5+0.5 year, 1.5+1.1 meter, 40.5+6.3 kg and youth 16.3+0.6 year, 1.7+1 meter, 69.6+4.8 kg. The program included endurance, strength and flexibility training 3 times per week for 12 weeks. Agility, coordination, sergeant jump, hand power, cardiovascular endurance, and modified push-up measured pre and post 12 weeks training. Data analyzed by one ways of ANOVA and Benfroni post hoc test showed that long jump, speed, shoulder elevate, sit-up at children group is better rather than adolescent and youth groups (P<0.05).