The celebration ceremony and the Congress of millennium of Ferdowsi to commemorate the 1000th birthday of Hakim Abolqasem Ferdowsi, the poet of the Shahnameh in 1313 A. H, is one of the most prominent manifestations of nationalism in time of Pahlavi the first. It was being held with the presence of Reza Shah and the most important political and cultural figures. Moreover, the construction and opening of Ferdowsi's mausoleum in Tus city marked a new chapter in the representation of Ferdowsi's lifetime and studies of Shahnameh at the national level with the aim of strengthening the ideology of imperial nationalism.The central issue of the present research is to investigate the why and how of holding this ceremony and to explain its relationship with the imperial nationalism dominating the political and cultural atmosphere of government of Pahlavi the first by taking advantage of the primary sources of this era. The study of the main historical sources related to this era declares that under the pretext of celebrating Ferdowsi’s status and dignity in the millennium of his birth, Pahlavi government considerably endeavored to increase the authority and legitimacy of the imperial nationalism of that era and through the exploitation of Shahnameh, it tried to introduce this famous epic and historical piece of Iranian literature as a document of admiration and devotion towards the kings by the Iranians throughout the history.