Despite the importance of physical activity is clearly accepted by all, motivation and participation in physical education declines with age. Therefore, the aim of this study is to investigate the relationship between the social support behavior of physical education teachers and motivation (absence of motivation) of student in P.E activities. This is a descriptive and correlation study. In doing so, we chose 381 one of high school students of Bookan city through multi-level cluster random method, as statistical samples, and to fill out, the questionnaire of motivation inventory – physical education (AI-PE) of Shen et.al (2010) with reliability (α=.78), and interpersonal behavior scale (IBS) of Pelletier et.al (2008) with reliability (α=.81). For data analyzing we used the Spearman correlation coefficient and Structural Equation Modeling (SEM). The results showed that there are negative and significant relationships between subscales of social support behavior (i.e. autonomy support, competence support, and relatedness support) with motivation, respectively (r=-0.207, r=-0.255, r=-0.216, p≤0.01). Also, according result of Structural equation modeling (SEM) social support behavior of physical education teachers effected on students’ motivation (0.21). According to the fact that, reduction of P.E teachers’ social support behavior may result students’ motivation, we recommend that P.E teachers increase the amount of social support, to finally improve students’ participation at school P.E activities.