Seo Geo-Jung was a great writer who lived during the reigns of King Sejong and Seongjong in Choseon dynasty. The aim of this thesis is to clarify the whole character of Dong-in-si-wha through the analysis of it s contents. This deals with just it s problems in the range of quotation poem s character, points of selecting poems, essential methods of criticism, meanings of poems, and poetic history (on the point of poets) in Dong-in-si-wha. The main points of this thesis are as follows; First, Dong-in-si-wha was compilated under the historical background of the growth of Sajanghak(詞章學) with the aim of developing the formulation of our poetry and to state his pragmatis theory that had been unilized for describing the moral rearmament. Second, Analyzing it s contents, we find that Seo was fond of seven syllabled poems and Dang-song s poems in China, especially Du-bo s and So-sik s, because of the tendency for setting values on Dang-song s literary culture and reverences for Du-bo s poem s at that time. Third, the methods of criticism in Dong-in-si-wha are comparative critics, intuitives, and pragmatics. Seo uses overwhelmingly comparative critics, which compare our poetry with those of Chinese. So he insists that our poetry should be valued highly as much as those of Chinese. With the original criticism which clarified effections of poets and writings, we can see that they persuited highly literary world. Intuitive criticism contains the emotions ;of poets in short syllables. It criticises the Chinese poetry s nature with short and connotative terms, and .is also the same way of criticising the classical poems. Pragmatic criticism treats the theme of poetry s utility. It contains that poetry purifies human nature(性情), trains human mentality(心性), helps enlightenment(敎化), and is necessary for diplomacy(外交). Fourth, researching the tendency Seo s poetic criticism, we can find that Seo laid a greater emphasis on contents than on formations by studying Dong-in-si-wha, because he chiefly criticised that poetry contains the emotions of the writer not the structure and tone in Chinese poetry. Fifth, Seo s theory of literature can be summed up with the theory of pragmatics, disposition, and rhetorics. Theory of pragmatics is the same of confucious that values for the traditional customs which treat the function of purification of the human temperament, train human mentality, help enlightenment, and is needed for diplomatic intercourses. Theory of disposition means the poet s human nature and the writer s personality shows the thematic elements in his poems. Seo treated those aspects eventually in Dong-in-si-wha. Theory of rhetorics the method of versification. It includes the use of past events(用事), the use of fresh & significant poetic terms (淸新하고 含蓄的인 詩語), following the past(踏襲) carving & chiseling in poetic terms(點化) and polishing up(推敲). But he never allowed imitation, overcarving & chiseling in poetic terms, and ambiguity in poems. Sixth, Dung-in-si-wha gave the readers raptures on studying the Korean classical poetic history for along time. Dong-in-si-wha contains earlist pure poetics effected by China and Koryeo dynasty, helped the developing our own poetics, and influenced poetics in later generations. Above all, Dong-in-si-wha was the earlist pure poetics that established the poetic theoty variously, and the thought of Seo represents the consciousness of Koreans. It had a great effect on editing the pure poetic magagines later on.