From the victory of the Islamic Revolution on February 11, 1979 to the referendum and approval of the Constitution on December 3, 1979 was a period of nine months and twenty days. The four major political trends (Islamists, the Leftists and socialist, liberal nationalists, and the eclectics) tried in different ways, in the process of drafting and approval of the constitution to incorporate their political-intellectual demands into the text of the constitution. This paper is an attempt through "historical review" and "process tracing" to study the most important concerns of political trends in the process of drafting and approval of the constitution. The results of this study show that, the main concern of the contributing political trends in the process of approval of the constitution was the relationship between Islamic and republican aspects of the system. The text of the 1979 constitution stipulated a delicate balance between Islamism and Republicanism aspects. Islamic was stipulated in the content and republicanism in the form of the system.