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In this correlational study, physical activity of girls’ has been predicted using ecological approach. For this purpose, 374 girls aged 10-12 years selected and completed Self-report questionnaire and physical activity children with reminders 7 days (PAQ-C), Perceived physical competence questionnaire (PPFS), Perceived School Climate Questionnaire for physical activity (Am & et al,2005) and Social Support Questionnaire (Grier and et al, 2008). The BMI index and Lincoln Oseretsky Motor Skills Test was calculated for all subjects. Multiple regression analysis showed Children's fitness, physical competence, perceived climate of the physical environment and social support of  friends and family (social environment) are significant predictors for amount of children's  physical activity (P <0.5). In this regard, based on effect coefficients it would be say that Fitness (10%), physical competence (15%), Motor Skills (12%), physical environment (23%) and social environment (24%) can predict children's physical activity. According to results, it would be suggested using the well- known ecological variables to predict children's activities.