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Tarjoman al-Balaghah written by Omar Radoviani, as the oldest Persian book on eloquence and criticism, holds a special and prominent stand among works devoted to the subject.It is the main source and reference for significant Persian books on eloquence such as Hadaeghat al-Sehr and Al-Mo'jam, which were compiled later .It was the first attempt to understand and establish Persian literary devices.The present study is devoted to a structural review as well as  an appraisal of the innovation and imitation of the book.To this end, we started with its main source, namelyMahasen al-Kalam Fi  al-Nazm va al-Nasr written by Marghinani, and analyzed its configuration, definitions, titles of literary devices, indexes,  and examples.Then, a few chapters of Mahasen-al-Kalam were compared with its main source,Al-Badi'written by Ibn-al-Mo'taz.We proceeded to review the structure of Tarjoman al-Balaghah, the way literary devices were organized, and how it was influenced by Mahasen al-Kalam.We concentrated on the similarities and differences between the two to get acquainted with indexing of literary devices based on the main reference, the alterations, as well as added devices in new classifications along with Persian examples.These enabled us to observe and explain the formation and development of Persian eloquence from the very beginning.Our findings indicated that although Radoviani was directly influenced by Mahasen al-Kalam, he added new devices and categories which were absent from Mahasen al-Kalam, and scholars in the field of eloquence used his book as a model for compiling new books.His innovations included utilizing a treasure of Persian names and poems by his own efforts.Although Radoviani adapted parts of Mahasen al-Kalam, he used a new structure, and his simple and fluent work took a pleasant Persian format.