Khosrow and Shirin, Nizami Ganjai's song, is one of the most famous and influential stories in Persian lyrical literature.Despite its great popularity, the source of this poem is ambiguous. The purpose of this research is to identify and introduce the sources of Nizami in composing the poetry of Khosrow and Shirin. In this article,the opinion of Nizami about the truth of the story has been expressed in descriptive-analytical way and according to the available historical texts and evidence and the analysis of the opinions presented,what was found about the sources of Nizami in the writings of Khosrow and Shirin has been analyzed and the final result has been announced according to the rhythm and history of the poem in Pahlavi literature.Regarding the sources of the story of Khosrow and Shirin, researchers have followed two opinions.A group considered it an imitation of Khosrow and Shirin mentioned in Ferdowsi's Shahnameh, and others considered it an imitation of Vis and Rāmin.The findings indicate that this story has a Pahlavi origin and was created by the surviving Parthians during the Sassanid era. which was on the tongues in Aran and Barde region and Nizami, while knowing the Pahlavi language, had the poem in mind as it was common in popular literature and in the Burda, and refined it until it reached us as it exists and if anything contrary to historical truth is observed in the poem, it is the responsibility of the creators and narrators of the story.