Iranians were the people who lived in the land of Great Iran in ancient times, in their social relations with each other and with the neighboring countries and with the people of the world of those days, they had wars, peaces and reconciliations, friendships and relationships. This behavior and their relationships and belief, which is history as the preserver and guardian of the documents of the past, has been preserved for the future generation. The ancient Iranians, for whom Ardeshir Sasanian used the word Iranshahri for the first time, had thoughts and ideas to express their opinions, beliefs in establishing relations with others, in the manner and ritual of governance and statecraft. Historians, poets and writers have been influenced by these ideas. Especially the poets of the 4th and 5th century were more influenced by it in their epic works, one of them is the famous Iranian poet Asadi Toosi. Asadi Tusi's Gershasp Nameh is the most important heroic and epic text after the Shahnameh. Although its subject is wars and heroic performances, it contains important and effective elements in the formation process of Iranshahri's ideas. Various topics and elements that have happened throughout history in the thoughts of ancient Iranians and the long-standing beliefs of Iranian citizens in their daily lives have a prominent appearance. The purpose of this research is to identify and analyze the intellectual foundations of Iranshahri as one of the coordinates in the intellectual level of this valuable work. Now this question is raised, what were Iranshahri's beliefs and thoughts in this book? And what has been reflected? In order to answer the questions in this research, which is analytical-descriptive and based on library studies, topics and elements such as "minorism, theology and religious orientation, Shah Armani, reconciliation and friendship, pact, oath, prophecy, catacombs, magic , fate and destiny" which was one of the main intellectual bases of Iranians and ancient Iranians, based on "Gershasp Name" and reference to "Shahnameh", "Bahman Nameh", "Barzonameh", "Faramarznameh", "Bano Ghassab Nameh" and "Detailed Court" has been examined and analyzed. By studying and examining Gershasep's epistles and epic poems in the Khorasani style, we can conclude that there are few parts of his poems that are not influenced by Iranshahri's ideas. Garshasp, the book of Esdi Toosi, travels, stories, wars, and performances, which are the result of the presence of Gershasp, the mythical warrior of Iran. Events have taken place in it, and there have been effective elements and phenomena, and beliefs that the people of Iran have fully believed in. In this work, the literary master has shown himself in the best way and these themes and elements in Asadi's book have been manifested as the second and best literary work of Khorasani style. And compared to the works of other epic poets of this style, it has been reflected in the best way.