The issue of Imamate has long been a subject of concern for renowned Islamic theologians and commentators. Islamic sects have not disagreed on any religious issue as much as the issue of Imamate. The difference between Shia and Sunni is not only in the person of the successor of the Prophet; rather, in each view, "Imam" has a special meaning, concept, and position that distinguishes these two sects from each other. Although much research has been conducted in this category, one of the research gaps in this field is the lack of proper use of modern research methods. One of the appropriate methods for accurately and systematically delineating the issue of Imamate in Nahjul-Balagha is the method of content analysis. Given the importance of the subject, the present study seeks to answer the question of which characteristic does Imam Ali (AS) consider most important for an Imam? In this regard, first 110 propositions were selected from the text of Nahjul-Balagha and in a table opposite each text, basic themes indicating different dimensions of Imamate were included, and each was placed under more general headings. Finally, by extracting 29 basic themes, 4 unifying themes, and 3 comprehensive themes, it was concluded that more than 70 percent of the themes are dedicated to the characteristics and attributes of the Imam, of which the most frequent is the Imam's possession of divine knowledge.