This dissertation proposes a research on the On Christian Doctrine, by Augustine of Hippo, about practical theology in its homiletic field. Therefore, the forth book of his above mentioned work was analyzed, highlighting his rhetorical styles presented. Preaching models are three (triplex dicendi genus) and are named and worked by him, as: simple style (dictionis submissae), moderate style (dictionis temperatae) and sublime style (sublime dicendi). This investigation on art of preaching, based on the bishop of Hippo, aims to contribute to the practice of contemporary preaching. For this, some steps were taken in order to organize the text. After introducing the subject, a historical analysis of Augustine s life was carried out, seeking to highlight the influences he lived in the field of his rhetorical training as important part to understand the nature of his writing and speaking practice as a pastor. The second stage of the research sought to understand each style covered in book IV by the hiponense bishop. Each genre (simple, moderate, and sublime) was examined as presented, with a view to its contribution to preaching in the 21st century church environment.