This article is to explain the policies that have been undertaken by government of Iran in foreign affairs since Islamic Revolution (1979). Although principles underlined in Constitution of Iran have been followed by Islamic Republic of Iran; but elected presidents have interpreted the principles variously. So, different approaches of foreign policy with different outcomes have been followed by presidents that had been chosen in presidential elections. In this article, we tend to explain the changes that caused by the presidents in foreign policy of Iran since Islamic Revolution. The article is written in tow main parts. In the first part, we are going to summarize the main approaches of foreign policy in Iran since Islamic Revolution and influence of them on Iran’s foreign policy in different periods; and in second part, we will explain foreign policy of Iran during presidencies of Ali Akbar Rafsanjani, Seyyed Mohammad Khatami and Mahmoud Ahmadinejad.