In the present paper, the analysis of the background and sociological reasons of the defeat of the Sasanian 's emperor  has been examined by Ferdowsi's Shahname. Some of these factors have been pointed out by historiographers, like war for power by the Sasanian 's emperor. But Ferdowsi has new viewpoints about these problems like women’s reign. Some of the reasons have been recognized by Ferdowsi like national origin and women's reign. Although the selection of the starting point of the discussion very difficult but for some reasons, which are mentioned in the text of the research, Khosrow Parviz's reign is the starting point of this discussion.