The rise and fall of the centralized system of the Sasanian Empire cannot be explained without examining the association of the Mobadi (Zoroastrian clergy) with it. The Zoroastrian clergy gradually became more organized and powerful from the middle years of the Parthian rule, and eventually, following the rise of the Sasanian dynasty to a high position, that is, alongside the monarchy, it began to influence the domestic and foreign policies of Iran during the Sasanian era. This authority was especially derived from the deep social influence of the clergy, which relied on the customs, traditions, and the doctrinal and legal system of Zoroastrianism. The main issue of this research is to explain the role and position of Kartir in a period of the Sassanid era. In it, an attempt has been made to address the role of Kartir in the structure of Sassanid religious politics. In the present article, information has been collected in a library manner and the research method is descriptive-analytical. This research has shown that: One of the classes of Sassanid society was the clergy or Asrons, whose head was among the privileged class of society. Among the Zoroastrian clergy who experienced the Sassanid monarchy (Azardshir to Nersi), was Kartir, who was able to enter the ranks of the elders of Sassanid society due to his actions, activities, ability, and possibly genius and charismatic personality. He tried to give personality and credibility to the institution of Zoroastrian clergy and to be effective in the formation of the official religion of Sassanid society and its religious structure. And upon the coming to power of Nersi, the measures he took, or in fact the system he had organized, if not completely, then faded away, and then he himself disappeared and was lost in history.