Introduction: Osteoporosis is a metabolic bone disease. This complication will reduce bone mineral density (BMD) and reduce bone strength. The purpose of present research was to study osteoporosis and its relative factors among student of Iranian Army. Methods: This is a cohort research conducted on two groups including 100 students of the cadet school and students of AJA medical school. The status of all participants was tracked for 5 variables including vitamin D, calcium, Femoral neck BMD, Total lumbar spine BMD, and Total hip BMD for a period of six months. Results: This was a cohort research conducted on 200 participants in 2 groups consisting of the cadet school students and students of AJA medical school. The participants aged from 18 to 24 years old with an average age of 20.08 ± 1.06 years. The results obtained through studying the five variables indicated that after a six month follow up period, only vitamin D and calcium levels among the cadet students had increased significantly compared to the first assessment (P-value<0.05). Other variables failed to exhibit a significant change within this period (P-value>0.05). Regardless of statistical significance, the general trend of change among cadet students indicated increase, but a decreasing trend was observed among AJA medical school students. Conclusion: Exposure to sunshine and physical activities play a major and significant role in increasing vitamin D and calcium levels. Otherwise, vitamin D deficiency and unfavorable consequences such as osteoporosis are inevitable.