Communication includes overall signification activity of human. And phenomena of literature give good materials to study the aspect of communication. Especially genres of literature have the character of media for communication and genre-selection is result of interaction of knowledge about the object, the attitude of speech, the relation with audience and the channel of communication so on. The purpose of this article is making the principle of genre-selection clear. For this aim I selected Kyung-Gi-Che-Ga(景幾體歌) and Si-Cho(時調) dealing with O-Ryun(五倫). And as a result, I could discover that Kyung-Gi-Che-Ga(景幾體歌) is selected in the principle of confirmation and Si-Cho(時調) is selected in the principle of delivery. Like this, in spite of the same theme different genres were needed according to the aim of communication. This phenomena can give important suggestion to the understanding of communication as well as that of classic literature. More interest in the genres as media for communication is needed.