Gungmunjeongri, written by Bong-Un Lee, is the first research book about Korean writing to be published since Hangeul (the Korean alphabet) became the official national script of Korea. In this study, we compared and contrasted Bong-Un Lee’s Gungmunjeongri, compiled in January 1897, with Gyu-Dae Lee’s Gungmunjeongri and estimated that Bong-Un Lee’s work was written before Gyu-Dae Lee’s. Bong-Un Lee’s Gungmunjeongri and Gyu-Dae Lee’s Gungmunjeongri were largely similar in terms of the table of contents, as well as the method and basis of analysis and notation, but differed in how the long sounds were written. Bong-Un Lee’s Gungmunjeongri attempted to understand and analyze syllables through the traditional classification criteria of purity and impurity, recognizing the long sounds of the Korean language and devising a system of long-sound notation. It was difficult for the notation system to be used broadly because its basis for analysis was not rational. He attempted academic analysis for Korean languages and Korean writing. and there cognition and classification of conceptsand the categorization of them having oppositional relationships are identifiedas academic thought processes in Gungmunjeongri. Despite its lack of systematic completeness, Gungmunjeongri is historically significant because it is the first research book that devised and published a notation system for Korean writing since Hangeul became the country’s official script.