The influence of exercise training on anabolic hormones is especially important for growth and development in childhood years. The aim of this study was determine effect of 8 weeks of swimming training on secretion of growth hormone in 9-11 years old boys. To test the research hypothesis, the people who were willing to cooperate with the investigator randomly assigned to experimental group (n=15: age: 9.33±0.30, height: 130.46±7.53, weight: 27.04±7.39) and control group (n=15: age: 9.39±0.39, height: 133.53±7.52, weight: 27.15±4.92). Experimental group participated in 8 weeks swimming training with intensity of 45-65% HRmax for 3 times per week and 1 hour per session. During this time control group did not participate in this protocol and continue to routine activity. Fasting blood sample were collected 48 hours before and after of 8 weeks swimming training to assess serum growth hormone. 8 weeks swimming training led to significant increase on growth hormone in experimental group (P= 0.000). But increase growth hormone in control group not significant (P= 0.383). In result, 8 week of swimming training led to significant increase on secretion growth hormone in 9-11 years old boys.