Chain reactions refer to the consecutive behavior of actors in the international arena, in which the acting action leads to another reaction and finally puts their relations in a certain direction. These hierarchical behaviors will be mostly equal or wider and are formed based on their understanding of each other's intentions. In recent years, the activism of Saudi Arabia and Iran has traveled a path from breaking off relations to re-establishing them, which mainly stems from their perception of each other's intentions. The ups and downs of the relations between Iran - Saudi Arabia in the Middle East have always had significant effects on the general relations of the region. Different religious and linguistic identity and non-complementary economy and the security view of the parties on their activism against each other, the relations of these two regional powers have led them to compete with each other in the best conditions. The purpose of this article is to investigate and analyze the relations between the two countries from the perspective of "chain reaction" and we are looking for an answer to the question of how the two countries' understanding of each other's behavior led to a sequence of reactions and how it ultimately affected their relations. It seems that the two countries' understanding of each other's behavior in the past has led to a sequence of negative reactions that ultimately led to the termination of their relations, and on the other hand, efforts to reduce tensions and common understanding of the higher cost of hostile relations in comparison Normal relations have caused the desire of both parties to re-establish relations