The purpose of this paper is to clarify the tendency of New Confucianism reflected in the literature written Chinese characters during the last period of Koryo dynasty, focused on the literary worky by Lee Sung-in. The major contents of this study is as following: 1. The new Confucian philosophy was introduced into Koryo dynasty by An Hyang and paeck I-jeong at the last period of Koryo dynasty and circulated by Jung Mong-ju and Lee Sung-in who were scholars of Sunggyungwan (Royal Academy at the period). When he gave lecture through books on confucianism, the latter made more emphasis on enthical aspects than literary ones, even though both ethical and literary elements were contained in the books. 2. At first Lee Sung-in was interested in such great thinkers as Budha and Laozu, but he rejected the previous thoughts and had more interest in New Confucian philosophical ideas after he became the royal academy member. 3. He believed the importance of this paper that Lee Sung-in emphasized the enlightening aspects in the way of teaching Confucian ethics. 4. Lee Sung-in`s 11 poems, "Chuyagamhoe"(Meditation in Autumn Night, 秋夜感懷), must have been greatly influenced by Chuja`s 20 poems, "Chaegugamhung" (Speculation in one`s study room, 齊居感興). Therefore this article summarizes that Lee Sung-in as one of the representative writers during the last period of Koryo dynasty was inclined to deal mainly with the themes of the New Confucianism because of the influence of his period.