Abstract: Physical activity is an important factor in attaining bone mass. However, the basic mechanisms of this effect are not fully understood. The present study was performed to investigate the effects of 9-weeks high intensity (70-80% of maximal heart rate) aerobic exercises on hormonal concentrations and Marker of metabolism of bone formation in young women. A total of 22 healthy, sedentary female volunteers aged 27.13�3.69 years divided in to 2 groups control (n = 11) and experimental (n = 11) using random sampling. The experimental group performed an activity for 9 weeks, 3 session per week and each session lasted 45 min with the intensity 70-80% of maximal heart rate, but the control group did not participate in any intervention. For measuring enzymatic and hormonal factors, from each two groups of experimental and control blood samples were taken just before and after exercise program. PTH and E₂ activity measured by ELISA and ALP activity measured DGKC methods respectively. We also used Paired t-test and ANCOVA to analyze the data (p<0.05). The results showed that 9 weeks high intensity aerobic exercises increased significantly in both PTH and ALP (p<0.001) and E₂ (p<0.018) in the experimental group in comparison with the control group. Research findings shows that 9 weeks aerobic exercises causes considerable changes in PTH, E₂ and ALP. Result this study suggest physical activity programs with specific intensities utilized in present research, can be used as a prevention factor of osteoporosis in young women.