The present study seeks a comparative study of the nature and function of political parties in the political thought of Ayatollah Shahid Beheshti and Ayatollah Mohammad Reza Mahdavi Kani. Paying attention to the commonalities and differences between these ideas and different views and descriptions of the quality of the political party, will lead to a better understanding of these ideas in the face of the party issue, and the result of that comparative analysis will increase party knowledge in the existing party system. Therefore, the main question of the present article is what is the nature and function of political parties in the Islamic Republic of Iran from the perspective of Ayatollah Beheshti and Ayatollah Mahdavi Kani and their similarities and differences. To get the answer; Three components of the thinker and provider of the theory, the audience, and the context or historical context have been considered; The descriptive-comparative method has been used to analyze and classify the collected data based on the library method. Therefore, the present article; After explaining the main characteristics, in two sections, the nature and function of Western political parties, went to the views of these two thinkers, and their views were read and compared in these two sections. The findings of this study show that despite the commonalities of the two thinkers in the substantive and functional part of the parties, there are also distinct aspects that are specific to the thought of the thinker who is noteworthy in determining his party position