Since its emergence, comparative literature has gone through various stages and theorized in different ways. Theorists and scholars have defined comparative literature according to the social conditions of their time and based on their perspective, goal and knowledge of literature. They have studied literary works of other nations either from an equal, or from a superior or inferior point of view. Comparative literature, however, is the result of the bond and common heritage of all people or what the German poet Goethe calls the world literature (Welt literature). Before its formal and academic appearance in universities, this common knowledge existed among people as part of trade relations, journeys, translations, and even destructive and ominous events such as wars. Since every nation has a role in the emergence of global culture and civilization, comparative literature has turned into a common heritage for all nations, and many countries have defined and interpreted it from their own special perspective, and defined a set of standards and principles for it. This article tries to explore the conceptual changes that comparative literature has gone through in different literary schools (French School, German School, American School, East European School, etc.) The writer will try to introduce elements influential in the emergence of various concepts and their dissemination in order to explain the status, importance and role of Persian literature in the global common heritage as well as its appeal to people of different nations.