Considering the importance of sufficient physical activity in military personnel, this study was designed to determine the levels of this activity and factors influencing it among personnel of a military center in Iran. This cross-sectional method on 191 individuals randomly selected from entire staff working in a military center. A self – report valid and reliable questionnaire was applied to collect the data. The collected data was analyzed using SPSS software, descriptive and analytical statistics. According to the findings of the study prevalence of low, moderate and high levels of physical activity by study population was 35.1%, 19.4% and 45.5% respectively.A significant positive association was seen between levels of physical activity with both knowledge (P=0.001) and gender (P=0.022). However, the association between, physical activity, with other studied factors such as age, job, and level of formal education was not significant. The most important factor of physical inactivity among participants was lack of enough free-time. On the other hand, accessibility to facilitates, organizational exercise, providing physical equipment's in job settings, and having free-time were the most important factors to promote the levels of physical activity, mentioned by the subjects. On the basis of the findings, especially considering the prevalence of the low level activity, 35.1%, and other documents supported this finding, one may conclude that performing educational program about to physical activity among military personnel seems necessary. To develop and promote enough equipment's and facilitates to increase the chance of sufficient physical activity among personnel is very important.