This paper has carried out a study on “Children head theory” and “Thatched cottage biography”, the two hanmun compositions on Kim Jin Yang published in the late Goryeo period. By studying the texts, the relationship between Kim Jin Yang and the two authors, and the creation date, the author of this paper has analyzed the structures, forms, styles, and writing tactics of these two compositions, trying to investigate the differences in between. An conclusion is drawn that the difference of these two compositions lies in their genres, one is "theory" and the other is "biography ". Kwon Geun and Lee Sung In eulogized Kim Jin Yang not only ecause of their friendship, but his frugality which is advocated by the scholars. Kwon Geun’s “Children head theory” described the liberal, high-spirited and vigorous young Kim Jin Yang by using a pleasant tone and a lively atmosphere. This composition is different from the traditional ancient Chinese "theory", which is much more like a “miscellany”, this is the Goryeo type of "theory". The Lee Sung In’s “Thatched cottage biography” describe the later years of Kim Jin Yang, so the atmosphere of this article is quite plodding, aiming at sketching out Kim Jin Yang’s aloofness and he can take the rough with the smooth even after his dismissal. This composition is also different from the traditional ancient Chinese "biography". Both two compositions not only helped to research the Goryeo scholar Kim Jin Yang, but also has a great importance for study the hanmun "theory" and "Biography" during the transition period from the end of the Goryeo to the beginning of the Chosun.