Iran-Russia relations have fluctuated a lot in the last two decades, so that after a period of lack of dynamism and stagnation between 2005 and 2013, the relations between the two countries, in 2013 to 2018, have shown great convergence in some aspects of international politics. In this regard, the present study, using descriptive and analytical methods, seeks to answer the question of how the relations between Russia and Iran in the 80s and 90s can be explained? To answer this question, the James Rosena continuity model has been used. In other words, the purpose of this study is to explain the causes of fluctuations in Iran-Russia relations based on the variables of the level of micro and macro analysis of the James Rosena continuity model. Findings show that Iran-Russia relations have experienced different conditions in these two periods, while in the first period their relations were relatively stagnant and static, in the second period these relations have become more dynamic and active, and macro-level variables such as common interests in Syria and Iraq, confronting US hegemony in the Middle East, sanctions, and gaining a balance of power with the United States have been major drivers of change in bilateral relations. The results of this study also show that the more active the variable of the international system, the more inclined Russia and the Islamic Republic of Iran are to cooperate with each other.