The purpose of this study was to predict the physical activity of students. The research community included all students aged 11 to 18 years old in public schools in Tehran during the first semester of the academic year of 2018-2019 which is selected by the sampling method. In this research, in order to measure the variables of the research, Godin and Shefard athletic exercise questionnaires (1985), Self-efficacy of physical activity and social support of Norman et al. (2005) and the expected outcomes of the exercise of Reconik et al. (2000) were carried out. The research results showed that there was a positive and significant relationship between social supports and social self-efficacy with physical activity, but there was no significant relationship between exogenous outcome and physical activity. Also, the results of multiple regression showed that social support and self-efficacy explain 14.5% of the total variance of students' physical activity changes and social support is a stronger predictor of self-efficacy. In order to increase physical activity adolescents can be used as an important factor in any intervention program of social support, especially parents and friends.