The agricultural sector as one of the most important sectors in the process of development has always had a special status in world economy. However, relative decrease of the share of agriculture over the recent decades often leads one to believe that agriculture can be ignored in favor of those sectors which have a faster progress, whereas, on the contrary, in order to accelerate favorable economic transition agriculture must be encouraged. Therefore, this research seeks to study the role and effect of the agricultural sector in comparison to other sectors such as industry, services, mining and commerce on variables such as GDP, the remnant of bank facilities and credit organizations, total petroleum exports in Iran during the past 15 years. Research methodology is applied and of descriptive-correlational type. Data collection tool is previous documents and evidence. Data analysis method is step-by-step regression. The results of the research indicate that in the first, second and third regression models agriculture respectively has the third, first and second status in regard to level of effectiveness.