The aim of this research was to study the relationship between socio – economic status and the rate of physical activity in students of Shahid Chamran University of Ahwaz. This research used a descriptive correlative approach which was performed by a field method. Statistical population included all undergraduate students in 89-90 school year (N=9175); 370 students were determined as the sample via stratified random sampling method. A researcher-made questionnaire in three parts (individual characteristic, socio-economic status and rate of physical activity) was used to collect data (?=0.71). For data analysis, descriptive and inferential statistics methods (Pearson and Spearman correlation coefficient, multivariate regression) were used (P?0.05). Findings showed that with regard to socio-economic status, 51.7% of students were in middle class, and only 1.4% belonged to the high class. Mean physical activity in girls and boys was 46.52 and 68.12 minutes per week respectively. 80% of students had physical activity and sport in their dormitories. Also, there was a significant positive relationship between the socio-economic status (p=0.001, r=0.277), income (p=0.001, r=0.245), economic class (p=0.028, r=0.152) and father's educational level (p=0.001, r=0.300) with the rate of students' physical activity. Analysis of multivariate regression showed family income (p=0.001, t=3.616) and father’s education (p=0.008, t=2.70) as the strongest factors to predict the rate of physical activity respectively. Overall, as the majority of students were in middle class and their physical activity was performed in dormitories, it seems that university authorities must develop and extend facilities and sport clubs especially in dormitories to maintain health and freshness of students who are the future of our societies.