Writing the grammar of a language is one of the most significant outputs of linguistic studies. In Iran, it is Avicenna (Ibn-e Sina) who is credited with the first such compilation of the Persian language. Understanding the weaknesses associated with the traditional trends of grammar writing in Iran, contemporary Iranian linguists adopted the modern Western approach following the Chomskyan Turn thus attempting to work out a grammar for Persian. Accordingly, this study investigated the scientific theory of grammar writing in Iran through a descriptive-analytic method, using the transformational-generative theory. In addition to reviewing the stances of Iranian grammarians, the paper specifies and describes grammars of different kinds through a typological approach so as to attain a new classification of grammar writing paradigms in Iran. The findings of this research show that grammar writing approaches in Iran are divided into three paradigms, namely, traditional, structural, and scientific. Manuscript profile