In this article, by comparing the historical reports of the book Estirār al-Emām with the reports of non-Ismaili sources, an attempt is made to examine and analyze the validity of this book as a historiographical source in reconstructing the history of the Ismailis before 297 AH. The results show that a critical reference to Ismaili works along with non-Ismaili sources can be an important step in reconstructing the history of the Fatimids during the absence era and help to remove the historical ambiguities of this sect, especially in the period between martyrdom of Imam Ja‘far Sadegh (PBUH) until the Fatimids’ gain power in Africa. Comparing the reports of the book Estitār al-Emām with the reports of non-Ismaili sources show that, due to the secrecy of the Ismaili invitation during the absence era, some events related to the history of this sect in this period can reconstructed only through internal sources. It is an important fact that has neglected or not paid enough attention and led to inaccurate and sometimes contradictory accounts of the political and cultural history of this lost period of Ismaili history. Data collection in this article is in library method and data analysis is based on qualitative content analysis with a comparative approach