As one of the prominent literary works, Ferdowsi’s Shāhnāma offers the potential to be researched from different views. Part of these researches are grammatical studies. One of the language characteristics of each person that distinguishes their as language from others is the range of usage and meaning of prefixes especially verb prefixes. The comparison of the language of Daghighi and Ferdowsi from the point of view of prefix verbs, better defines the linguistic differences of these two poets. In this research, we have compared Goshtāspnāma, Daghighi’s 1015 verses included in the Ghoshtāsp section of the Shāhnāma, with 1015 verses by Ferdowsi in the Lohrāsp and Ghoshtāsp sections. The range of meanings of prefix verbs in Ferdowsi’s language is more than that of Daghighi, but in terms of quantity, more prefix verbs are used by Daghighi. In Daghighi’s language, the prefix frūd (فرود)is significantly used more often than in Ferdowsi’s. frūd āmadan (فرود آمدن) is the most frequent in Daghighi’s poetry and andar āmadan (اندر آمدن) is the most frequent in Ferdowsi’s poetry. The distance between the prefix and the root of the verb in Daghighi’s verse is three times more than that of Ferdowsi, but the reversal of the prefix and the root of the verb in Ferdowsi’s language is more than Daghighi’s. The prefix bar is the most frequently used prefix of both poets, which fits the epic tone and nuances as well as the Khorāsāni style. There are some difficulties in identifying the prefix verb in Daghighi and Ferdowsi’s language which requires precision and examination of other aspects of language.