In the course of the 7th century, Persia was overrun by victorious Muslim armies, and the Sasanian Empire(226~651) crumbled. The Arab conquest proved to be far more than military, for it introduced a new religion of Islam into Persian and opened an entirely new chapter in Iranian history as well. The characteristic belief of Zoroastrian religion of Iran disappeared, gone, too, were the class distinctions which had been the backbone of the Sasanian social and political organization. The Islamization of Persia brought about such deep and enduring transformation in the life and culture of the country. But from the 9th century, Persian language emerged again as the tool of a "Renaissance" of Persian literature. The greatest monument without doubt was "Shahnameh(The Book of Kings)" of Ferdawsi(completed in 1015), although the work of literary genius, is in substance the reworking of the national saga of the end of the Sasanian period. As the best example of Shahnameh, the Persian literature generally tends to be descriptive rather than dramatic, expressionistic rather than naturalistic, organic rather than architectural. The Shahnameh gives the history of Iran from the Creation down to its conquest by the Arabs in the 7th century. The first half tells of mythical and legendary kings and heroes, and the second half tells of historical personages. Through the study on the structure and function of each heroes and kings in the Shahnameh, we can analyze more accurately the characters of heros in the Kushnameh in which we can find very interesting stories on mutual relations between some Persian heroes and Silla royal families in the 7th century. The Kushnameh, an pre-Islamic Persian epic, gives us surprisingly many remarkable description on Silla Kingdom of the 6~8th centuries. Such main heroes in the Shahnameh as Abtin, Farānak and their son Feridun appear in the Kushnameh in different role and social circumstances. Abtin with his royal families migrated to Silla with the invitation of the king, through long and difficult expedition in Iran and China. Abtin married a Silla princess named Frarang and a most famous Persian hero Feridun was born. After the death of Abtin, Feridun returned Iraq to destroy Kus, a demon-king who had killed Abtin and Jamshid. Eventually, Feridun had Kus borne to Mt. Demavent chained and powerless. To the great joy of the many who had for so long suffered his tyrannies, Faridun repealed the cruel laws of Kus and bade every man live in peace and work in freedom. Of course Feridun informed the good news to his grandfather, the Silla king Tayhur. But Tayhur is already passed away and Karam became new Silla king with whom Feridun continued their friendly relations and cooperation. The Kushmameh can be the vital source for new interpretation of ancient Silla history and society, through which the study of Korean ancient history opens new horizon based on more vivid historical materials unknown. In this sense, the significant meaning of Kushnameh in studying Korean history is already emphasized by the previous articles. The main difficulty faced to us now is that how much Korean academia could accept the epic stories as historical sources. I firmly believe, however, e Persian poetry or epic speaks the language of the Persian heart, mind and soul, fully reflecting the Persian world view and life experience. To study Persian epics therefore is the important tool to understand the history of Iran and beyond at that time. By more systemic and long term research projects, the wide range of rich contents on Silla described in Kushnameh can be enlightened hopefully. This article is one of the research plans.